Single domain antibody binders of myc

Abstract

Disclosed herein are polypeptides comprising or consisting of anti-Myc single domain antibodies (sdAd), as well as bifunctional and dual-specific bifunctional polypeptides incorporating the anti-Myc sdAbs that induce degradation of a first and optionally a second biological target through the cellular proteasome mechanism. The disclosed bifunctional polypeptides generally comprise a first targeting moiety that includes the anti-Myc sdAb, and a second component that has ubiquitination function, and optionally a second targeting moiety targeting at least a second target protein. The binding of Myc by the first targeting moiety promotes ubiquitination of Myc by the second component, thereby labeling the Myc for proteasomal degradation. These bifunctional polypeptides may be used for the treatment of a disease in a subject, where the first and / or second targeting moieties bind a biological target(s) whose abnormal function and / or expression is associated with the disease.

Description

[0001] SINGLE DOMAIN ANTIBODY BINDERS OF MYC CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application Serial No. 63 / 597,283, filed November 8, 2023, the disclosure of which is hereby incorporated by reference in its entirety, including all figures, tables and amino acid or nucleic acid sequences. REFERENCE TO SEQUENCE LISTING The present application is being filed along with a Sequence Listing in electronic format. The Sequence Listing is provided as a file entitled Seq-List.xml, which was created on November 7, 2024, which is 924,266 bytes in size. The information in the electronic Sequence Listing is hereby incorporated by reference in its entirety. FIELD Aspects of the present disclosure related to novel polypeptides comprising single domain antibody binders of Myc (e.g., c-Myc). Aspects of the present disclosure also relate generally to bifunctional polypeptides that promote ubiquitin-mediated proteasomal degradation of desired biological target(s), for example Myc, and uses such as for the treatment of a disease associated with the biological target(s). Aspects of the present disclosure also relate generally to dual-specific bifunctional polypeptides that promote ubiquitin-mediated proteasomal degradation of desired biological targets, for example Myc and another target, and uses such as for the treatment of a disease associated with the biological targets. BACKGROUND Conventional therapeutics, such as small molecule and antibody inhibitors, operate by blocking or otherwise modulating the function of a therapeutic target (e.g., blocking an enzymatic or transcription promoting function). While many therapeutics belonging to this category have shown to be effective, confounding effects may arise as the therapeutic target is still present within the cellular milieu. Molecular glues and proteolysis targeting chimeras (PROTACs) are alternative classes of therapeutics that involve small molecule compounds that recruit E3 ubiquitin ligases to a therapeutic target, thereby inducing proteolysis of the therapeutic target through the endogenous proteasomal degradation machinery. The physical degradation of the target drives a therapeutic effect through the elimination of the dysfunctional and / or disease-associated target. However, design of these small molecule degraders involves significant screening and optimizations to identify chemical modalities that are compatible for binding to both the therapeutic target and E3 ubiquitin ligase. Identification of such small molecule degraders is particularly challenging for previously undrugged intracellular targets, especially proteins that lack enzymatic domains amenable to traditional small molecule screening and optimization. Further, the use of antibody derived binding moieties as to bind to target proteins such as Myc in the intracellular space (e.g., intrabodies) can be hindered by the highly reducing conditions of the intracellular environment which can disrupt the disulfide bonds required for proper mAb / scFv folding. Therefore, there is a need for target binding moieties that can function in the intracellular space, and can be employed in compounds designed to utilize a proteasomal degradation tactic to degrade target proteins, for example in the intracellular space. SUMMARY OF THE DISCLOSURE Disclosed herein are polypeptides comprising or consisting of an anti-Myc single domain antibody (sdAb), comprising or consisting of a VH domain of an IgG antibody, or a VHH, or VHdomain of a heavy chain antibody (HcAb). These anti-Myc sdAbs can be expressed intracellularly and can be employed as part of a designed to utilize a proteasomal degradation tactic to degrade Myc, and optionally one or more additional target proteins. Disclosed herein are bifunctional polypeptides comprising the anti-Myc sdAb that promote proteasome-mediated degradation of Myc. In some embodiments, the bifunctional polypeptide comprises a) an anti-Myc sdAb; and b) a ubiquitin-proteasome system recruiting domain (URD). In some embodiments, proximity of the bifunctional polypeptide to the target protein through binding of the targeting moiety induces ubiquitination of the target protein (Myc) via the URD, thereby promoting proteosome-mediated degradation of the target protein. Also disclosed herein are dual-specific bifunctional polypeptides that promote proteasome-mediated degradation of Myc and at least one second target protein. In some embodiments, the dual- specific bifunctional polypeptide comprises a) an anti-Myc sdAb (target binding domain) that is capable of binding to at least Myc; b) a second targeting moiety that is capable of binding to at least one second target protein; and c) a URD. Optionally, in some embodiments the polypeptides further comprise d) a first linker peptide; wherein the first linker peptide is positioned between the first targeting moiety and the URD; and / or optionally e) a second linker peptide, wherein the second linker peptide is positioned between the second targeting moiety and the URD. In some embodiments, proximity of the dual-specific bifunctional polypeptide to either or both of the target proteins through binding of the targeting moiety induces ubiquitination of one or both of the target protein(s) via the URD, thereby promoting proteosome-mediated degradation of the target protein(s). In some embodiments, dual-specific bifunctional polypeptide is in a “contralateral” configuration in which the first and second target binding domains are on either side of the URD, i.e., one is on the C-terminal side of the URD, and one is on the N-terminal side of the URD. In some embodiments, dual-specific bifunctional polypeptide is in a “tandem” configuration in which the first and second target binding domains are both on the same side of the URD, i.e., both are on the C-terminal side of the URD, or both are on the N-terminal side of the URD. Optionally, in some embodiments a linker peptide (a first or a second linker peptide) is positioned between the two target binding domains, and / or between a targeting moiety and the URD. In some embodiments, the bifunctional polypeptide or dual-specific bifunctional polypeptide comprises one or more localization sequences to direct the polypeptide to a preferred subcellular compartment (e.g., nucleus). Also disclosed herein are polynucleotides encoding for any of the polypeptides comprising or consisting of the anti-Myc sdAb, the bifunctional or dual-specific bifunctional polypeptides, or any portions thereof, provided herein. Also disclosed herein are pharmaceutical compositions comprising any of the polypeptides comprising or consisting of the anti-Myc sdAb, or the bifunctional or dual- specific bifunctional polypeptides provided herein and one or more pharmaceutically acceptable excipients, carriers, or diluents. Also disclosed herein are methods of treating a subject. In some embodiments, the methods comprise administering any of the polypeptides comprising or consisting of the anti- Myc sdAb, the bifunctional or dual-specific bifunctional polypeptides, polynucleotides, or pharmaceutical compositions provided herein to a subject in need thereof. For example, the methods may be for the treatment of a cancer. Also disclosed herein are methods of reducing the amount of a target protein in a cell. In some embodiments, the methods comprise contacting the cell with any of polypeptides comprising or consisting of the anti-Myc sdAb, the bifunctional or dual-specific bifunctional polypeptides, polynucleotides, or pharmaceutical compositions provided herein. In some embodiments, the cell is in a subject, and the polypeptides comprising or consisting of the anti- Myc sdAb, the bifunctional or dual-specific bifunctional polypeptide, polynucleotide, or pharmaceutical composition is administered to the subject. In some embodiments, the cell is contacted ex vivo, and after contacting the cell with the polypeptides comprising or consisting of the anti-Myc sdAb, the bifunctional or dual-specific bifunctional polypeptide, polynucleotide, or pharmaceutical composition, the cell is administered to a subject, optionally wherein the subject is also the source of the cell (e.g., in an adoptive cell therapy). Some embodiments provided herein are described by way of the following provided numbered embodiments: 1. A polypeptide comprising or consisting of an anti-Myc single domain antibody (sdAb), comprising or consisting of a VH domain of an IgG antibody, or a VHH, or VH domain of a heavy chain antibody (HcAb), wherein the VHor VHH domain comprises a VH CDR3 comprising or consisting of any one of SEQ ID NOs: 179, 195, 211, 219, 251, 267 or 283, optionally wherein the VH CDR3 sequence comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 179, 195, 211, 219, 251, 267 and 283. 2. The polypeptide of embodiment 1, wherein the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AX1X2X3X4X5X6X7X8X9X10X11X12EX13DY (SEQ ID NO: 299), wherein X1 is A, H, Y, I, or T; X2 is L or I; X3 is G, D or P; X4 is D, Q, G or E; X5 is Y, E or I; X6 is G, L or S; X7 is D,T, S or G; X8is A, G, F, or no amino acid; X9is I, G, or no amino acid; X10is D, G, T or L; X11is Y, A, F or G; X12 is S, D or N; and X13 is A, H, G or Y; or optionally a conservative substitution of any of the foregoing; wherein the CDR3 does not comprise or consist of any one of SEQ ID NOs: 143, 151, 159, 167, or 175. 3. The polypeptide of embodiment 1 or 2, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 177, 185, 201, 209, 217, 225, 233, 241, 249, 257, 265, 273, 281, 289; a CDR2 comprising or consisting of any one of SEQ ID NOs: 178, 186, 194, 202, 210, 218, 226, 234, 242, 250, 266, 274, 282 or 290; and a CDR3 comprising or consisting of any one of SEQ ID Nos: 179, 195, 211, 219, 251, 267 or 283; optionally wherein the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a.) SEQ ID NOs: 177, 178, and 179; b.) SEQ ID NOs: 185, 186, and 187; c.) SEQ ID NOs: 177, 194, and 195; d.) SEQ ID NOs: 201, 202, and 179; e.) SEQ ID NOs: 209, 210, and 211; f.) SEQ ID NOs: 217, 218, and 219; g.) SEQ ID NOs: 225, 226, and 219; h.) SEQ ID NOs: 233, 234, and 219; i.) SEQ ID NOs: 241, 242, and 219; j.) SEQ ID NOs: 249, 250, and 251; k.) SEQ ID NOs: 257, 218, and 219; l.) SEQ ID NOs: 265, 266, and 267; m.) SEQ ID NOs: 273, 274, and 267; n.) SEQ ID NOs: 281, 282, and 283; and o.) SEQ ID NOs: 289, 290, and 283; optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 177-179, 185-186, 194- 195, 201-202, 209-211, 217-219, 225-226, 233-234, 241-242, 249-251, 257, 265-267, 273-274, 281-283, or 289-290. 4. The polypeptide of any one of embodiments 1-3, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of FX1FX2X3X4X5MX6(SEQ ID NO: 297), wherein X1is T or D; X2is A, S, E, G or D; X3is D, T, G, E, V or S; X4is T, M, Q, A, H, Y, V or N; X5 is D, P or A; and X6 is G or S; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of AIX1X2X3X4X5X6X7YYADSVX8G (SEQ ID NO: 298), wherein X1 is S or no amino acid; X2 is G, A, P, R or S; X3 is S, D, T or G; X4 is G, A, S, or E; X5 is G, D, E, A or S; X6 is N, V, A, S, E, T, D or H; X7 is T or A, and X8is K or R; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of AX1X2X3X4X5X6X7X8X9X10X11X12EX13DY (SEQ ID NO: 299), wherein X1is A, H, Y, I, or T; X2 is L or I; X3 is G, D or P; X4 is D, Q, G or E; X5 is Y, E or I; X6 is G, L or S; X7is D,T, S or G; X8is A, G, F, or no amino acid; X9is I, G, or no amino acid; X10is D, G, T or L; X11is Y, A, F or G; X12is S, D or N; and X13is A, H, G or Y; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2, and CDR3 is not one of the following combinations: a.) CDR1, CDR2 and CDR3 of mycV.0300 (SEQ ID NOs: 139, 141 and 143); b.) CDR1, CDR2 and CDR3 of mycV.1300 (SEQ ID NOs: 147, 149 and 151); c.) CDR1, CDR2 and CDR3 of mycV.1500 SEQ ID NOs: (155, 157 and 159); d.) CDR1, CDR2 and CDR3 of mycV.3700 SEQ ID NOs: (163, 165 and 167); and e.) CDR1, CDR2 and CDR3 of mycV.6600 SEQ ID NOs: (171, 173 and 175). 5. The polypeptide of any one of embodiments 1-4, wherein the sdAb, optionally a VHH domain, comprises a VH FR1 comprising or consisting of any one of SEQ ID NOs: 180, 188, 212, 228 or 284, a VHFR2 comprising or consisting of SEQ ID NO: 181, a VHFR3 comprising or consisting of any one of SEQ ID NOs: 182, 190, 278 or 286, and a VH FR4 comprising or consisting of any one of SEQ ID NOs: 183 or 215, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a.) SEQ ID NOs: 180, 181, 182, and 183; b.) SEQ ID NOs: 188, 181, 182, and 183; c.) SEQ ID NOs: 212, 181, 182, and 215; d.) SEQ ID NOs: 188, 181, 182, and 215; e.) SEQ ID NOs: 228, 181, 182, and 215; f.) SEQ ID NOs: 188, 181, 278, and 183; and g.) SEQ ID NOs: 284, 181, 286, and 183; optionally wherein each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 180-183, 188, 190, 212, 215, 228, 278, 284 or 286. 6. The polypeptide of any one of embodiments 1-5, wherein the sdAb, optionally a VHH domain, comprises: a FR1 comprising or consisting of the amino acid sequence X1VX2LX3ESGGGLVQPGGSLRLSX4AASG (SEQ ID NO: 300), wherein X1is E or G; X2 is Q or R; X3 is L or V; and X4 is A or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1 is E, X2 is Q, X3 is L, and X4 is A or C; a FR2 comprising or consisting of the amino acid sequence SEQ ID NO: 301; a FR3 comprising or consisting of the amino acid sequence RFX1ISRDNSKNTLYLQMNX2LRAX3DTAVYYX4 (SEQ ID NO: 302), wherein X1 is T or S, X2is S or G, X3is E or A, X4is A, V, or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1is R, X2is S, X3is E, and X4 is A or C; and a FR4 comprising or consisting of the amino acid sequence WGX1GTQVTVSS (SEQ ID NO: 303), wherein X1is Q or R; or optionally a conservative substitution of any of the foregoing; optionally wherein X1 is Q. 7. The polypeptide of any one of embodiments 1-6, wherein the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288 or 296, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 177-179, 185-186, 194-195, 201, 202, 209-211, 217-219, 225-226, 233-234, 241- 242, 249-251, 257, 265-267, 273-274, 281-283, or 289-290, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 180-183, 188, 190, 212, 215, 228, 278, 284 or 286. 8. The polypeptide of any one of embodiments 1-7, wherein the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288 or 296. 9. The polypeptide of any one of embodiments 1-8, wherein the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AALGDYGX1AIDYSEADY (SEQ ID NO: 306), wherein X1is D or G; or optionally a conservative substitution of any of the foregoing; optionally wherein the CDR3 comprises or consists of any one of SEQ ID NOs: 179 or 195. 10. The polypeptide of embodiment 9, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 177, 185, or 201; a CDR2 comprising or consisting of any one of SEQ ID NOs: 178, 186, 194 or 202; and a CDR3 comprising or consisting of any one of SEQ ID NOs: 179 or 195; optionally wherein the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a.) SEQ ID NOs: 177, 178, and 179; b.) SEQ ID NOs: 185, 186, and 179; c.) SEQ ID NOs: 177, 194, and 195; and d.) SEQ ID NOs: 201, 202, and 179; optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 177-179, 185-186, 194- 195, or 201-202. 11. The polypeptide of any one of embodiments 9-10, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3X4MX5(SEQ ID NO: 304), wherein X1is A, S or E; X2is D, T, or G; X3is T, M or Q; X4 is D or P; and X5 is G or S; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISX1X2X3X4X5TYYADSVX6G (SEQ ID NO: 305), wherein X1is G or A; X2is S or D; X3 is G or A; X4 is G, D, or E; X5 is N, V or A; and X6 is K or R; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence AALGDYGX1AIDYSEADY (SEQ ID NO: 306), wherein X1 is D or G; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.0300 (SEQ ID NOs: 139, 141 and 143). 12. The polypeptide of any one of embodiments 9-11, wherein the sdAb, optionally a VHH domain, comprises a VHFR1 comprising or consisting of any one of SEQ ID NOs: 180 or 188, a VHFR2 comprising or consisting of SEQ ID NO: 181, a VHFR3 comprising or consisting of any one of SEQ ID NOs: 182 or 190, and a VH FR4 comprising or consisting of SEQ ID NO: 183, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a.) SEQ ID NOs: 180, 181, 182, and 183; b.) SEQ ID NOs: 188, 181, 190, and 183; and c.) SEQ ID NOs: 188, 181, 182, and 183; optionally wherein each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 180-183, 188 or 190. 13. The polypeptide of any one of embodiments 9-12, wherein the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 184, 192, 200, 208, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 177-179, 185-186, 194-195, or 201-202, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 180-183, 188 or 190. 14. The polypeptide of any one of embodiments 9-13, wherein the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 184, 192, 200, 208. 15. The polypeptide of any one of embodiments 1-8, wherein the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AX1LX2QELTGASEHDY (SEQ ID NO: 309), wherein X1 is H or Y; and X2 is D or G; or optionally a conservative substitution of any of the foregoing; optionally wherein the CDR3 comprises or consists of SEQ ID NO: 211. 16. The polypeptide of embodiment 15, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of SEQ ID NO: 209, a CDR2 comprising or consisting of SEQ ID NO: 210, and a CDR3 comprising or consisting of SEQ ID NO: 211; optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 209-211. 17. The polypeptide of any one of embodiments 15-16, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3X4MG(SEQ ID NO: 307), wherein X1is G or D; X2is D or E; X3is A or T; and X4is D or A; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISASX1X2X3TYYADSVKG (SEQ ID NO: 308), wherein X1 is G or S, X2 is D or A, and X3is X or E; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence AX1LX2QELTGASEHDY (SEQ ID NO: 309), wherein X1 is H or Y; and X2 is D or G; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.1300 (SEQ ID NOs: 147, 149 and 151). 18. The polypeptide of any one of embodiments 15-17, wherein the sdAb, optionally a VHH domain, comprises a VHFR1 comprising or consisting of SEQ ID NO: 212, a VH FR2 comprising or consisting of SEQ ID NO: 213 a VH FR3 comprising or consisting of SEQ ID NO: 214, and a VHFR4 comprising or consisting of SEQ ID NO: 215; optionally wherein each VHframework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 212-215. 19. The polypeptide of any one of embodiments 15-18, wherein the sdAb, optionally a VHH domain, comprises or consists of a sequence that is SEQ ID NO: 216, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 209-211, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 212-215. 20. The polypeptide of any one of embodiments 15-19, wherein the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to SEQ ID NO: 216. 21. The polypeptide of any one of embodiments 1-8, wherein the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AIIDDILTX1GTFDEGDY (SEQ ID NO: 312), wherein X1 is G or D; or optionally a conservative substitution of any of the foregoing; optionally wherein the CDR3 comprises or consists of any one of SEQ ID NOs: 219 or 251. 22. The polypeptide of embodiment 21, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 217, 225, 233, 241, 249 or 257; a CDR2 comprising or consisting of any one of SEQ ID NOs: 218, 226, 234, 242 or 250, and a CDR3 comprising or consisting of any one of SEQ ID NOs: 219 or 251; optionally wherein the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a.) SEQ ID NOs: 217, 218, and 219; b.) SEQ ID NOs: 225, 226, and 219; c.) SEQ ID NOs: 233, 234, and 219; d.) SEQ ID NOs: 241, 242, and 219; e.) SEQ ID NOs: 249, 250, and 251; and f.) SEQ ID NOs: 257, 218, and 219; Optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 217-219, 225-226, 233- 234, 241-242, 249-251, and 257. 23. The polypeptide of any one of embodiments 21-22, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FX1FX2X3X4X5MG (SEQ ID NO: 310), wherein X1 is T or D; X2 is A, E, D, S or G; X3is D, E or T; X4is T, H, Y, V or A; and X5is D, A or S; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISX1X2X3X4X5 X6YYADSVKG (SEQ ID NO: 311), wherein X1is G, P, R or A; X2is S or D, X3is G or A, X4is G, A, T or D; X5is S, T, A or V; and X6is T or A; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence AIIDDILTX1GTFDEGDY (SEQ ID NO: 312), wherein X1is G or D; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.1500 SEQ ID NOs: (155, 157 and 159). 24. The polypeptide of any one of embodiments 21-23, wherein the sdAb, optionally a VHH domain, comprises a VH FR1 comprising or consisting of any one of SEQ ID NOs: 220 or 228, a VHFR2 comprising or consisting of SEQ ID NO: 221, a VHFR3 comprising or consisting of SEQ ID NO: 222, and a VHFR4 comprising or consisting of SEQ ID NO: 223, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a.) SEQ ID NOs: 220, 221, 222, and 223; and b.) SEQ ID NOs: 228, 221, 222, and 223; optionally wherein each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 220-223, or 228. 25. The polypeptide of any one of embodiments 21-24, wherein the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 224, 232, 240, 248, 256 or 264, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 217-219, 225-226, 233-234, 241-242, 249-251, or 257; and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 220-223, or 228. 26. The polypeptide of any one of embodiments 21-25, wherein the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 224, 232, 240, 248, 256 or 264. 27. The polypeptide of any one of embodiments 1-8, wherein the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of SEQ ID NO: 267. 28. The polypeptide of embodiment 27, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 265 or 273, a CDR2 comprising or consisting of any one of SEQ ID NOs: 266 or 274, and a CDR3 comprising or consisting of SEQ ID NO: 267; optionally wherein the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a.) SEQ ID NOs: 265, 266, and 267; and b.) SEQ ID NOs: 273, 274, and 267; optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 265-267, or 273-274. 29. The polypeptide of any one of embodiments 27-28, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3DMG (SEQ ID NO: 313), wherein X1 is D, G or E; X2 is V, S or G; and X3 is S, N, or Q; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AIX1X2X3X4X5X6TYYADSVKG (SEQ ID NO: 314), wherein X1 is no amino acid or S; X2 is G or S; X3 is T, G, or S; X4 is E or G; X5 is G, D or E; and X6 is D, T or H; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence SEQ ID NO: 315; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.3700 SEQ ID NOs: (163, 165 and 167). 30. The polypeptide of any one of embodiments 27-29, wherein the sdAb, optionally a VHH domain, comprises a VH FR1 comprising or consisting of SEQ ID NO: 268, a VHFR2 comprising or consisting of SEQ ID NO: 269, a VHFR3 comprising or consisting of any one of SEQ ID NOs: 270 or 278, and a VHFR4 comprising or consisting of SEQ ID NO: 271, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a.) SEQ ID NOs: 268, 269, 270, and 271; and b.) SEQ ID NOs: 268, 269, 278, and 271; optionally wherein each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 268-271, or 278. 31. The polypeptide of any one of embodiments 27-30, wherein the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 272 or 280, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 265-267, or 273-274, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 268-271, or 278. 32. The polypeptide of any one of embodiments 27-31, wherein the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 272 or 280. 33. The polypeptide of any one of embodiments 1-8, wherein the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of SEQ ID NO: 283. 34. The polypeptide of embodiment 33, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 281 or 289, a CDR2 comprising or consisting of any one of SEQ ID NOs: 282 or 290, and a CDR3 comprising or consisting of SEQ ID NO: 283; optionally wherein the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a.) SEQ ID NOs: 281, 282, and 283; and b.) SEQ ID NOs: 289, 290, and 283; optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 281-283, and 289-290. 35. The polypeptide of any one of embodiments 33-34, wherein the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3AMX4(SEQ ID NO: 316), wherein X1is S or D; X2is S, E or D; X3is Y or H, and X4 is S or G; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISX1X2X3X4X5TYYADSVKG (SEQ ID NO: 317), wherein X1G or A; X2is S or D; X3 is G or A; X4 is G or S; and X5 is S, V or T; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence SEQ ID NO: 318; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.6600 SEQ ID NOs: (171, 173 and 175). 36. The polypeptide of any one of embodiments 33-35, wherein the sdAb, optionally a VHH domain, comprises a VH FR1 comprising or consisting of SEQ ID NO: 284, a VH FR2 comprising or consisting of SEQ ID NO: 285, a VH FR3 comprising or consisting of SEQ ID NO: 286, and a VHFR4 comprising or consisting of SEQ ID NO: 287, optionally wherein the combination of FR1, FR2, FR3, and FR4 is 284, 285, 286, and 287; optionally wherein each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 284, 285, 286, and 287. 37. The polypeptide of any one of embodiments 33-36, wherein the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 288 or 296, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 281-283, and 289-290, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 284, 285, 286, and 287. 38. The polypeptide of any one of embodiments 33-37, wherein the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 288 or 296. 39. The polypeptide of any one of embodiments 9-38, wherein the sdAb, optionally a VHH domain, comprises: a FR1 comprising or consisting of the amino acid sequence X1VX2LX3ESGGGLVQPGGSLRLSX4AASG (SEQ ID NO: 300), wherein X1 is E or G; X2 is Q or R; X3 is L or V; and X4 is A or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1is E, X2is Q, X3is L, and X4is A or C; a FR2 comprising or consisting of the amino acid sequence SEQ ID NO: 301; a FR3 comprising or consisting of the amino acid sequence RFX1ISRDNSKNTLYLQMNX2LRAX3DTAVYYX4(SEQ ID NO: 302), wherein X1is T or S; X2 is S or G; X3 is E or A; X4 is A, V, or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1 is R, X2 is S, X3 is E, and X4is A or C; and a FR4 comprising or consisting of the amino acid sequence WGX1GTQVTVSS (SEQ ID NO: 303), wherein X1 is Q or R; or optionally a conservative substitution of any of the foregoing; optionally wherein X1 is Q. 40. The polypeptide of any one of embodiments 1-39, wherein the sdAb comprises a VHH domain with a substitution at C22 of FR1 and / or C30 of FR3, optionally wherein the substitution is independently selected from a C to A and a C to V substitution. 41. The polypeptide of any one of embodiments 1-40, wherein the sdAb has a Kd value of less than 1x10-7and optionally at least 1x10-10, optionally wherein the Kd is 1.49x10-7to 5.56x10-9. 42. The polypeptide of any one of embodiments 1-41, wherein the sdAb has a Poly Specificity Reagent (PSR) score of less than 1, optionally less than 0.43, optionally less than 0.26. 43. The polypeptide of any one of embodiments 1-42, wherein the sdAb has a PSR score of at least 0.01, optionally at least 0.26, optionally at least 0.43. 44. The polypeptide of any one of embodiments 1-43, wherein the sdAb has a PSR score of 1 to 0.01, 0.43 to 0.01, or 0.26 to 0.01. 45. The polypeptide of any one of embodiments 1-44, wherein the sdAb has a melting temperature (TM) of at least 40℃, optionally at least 45.5℃, optionally at least 64℃. 46. The polypeptide of any one of embodiments 1-45, wherein the sdAb has a TMof less than 70℃, optionally wherein the TMis 45℃ to 65℃. 47. The polypeptide of any one of embodiments 1-46, wherein the sdAb binds, or binds at least in part, to at least a portion of amino acids 410-419 of MYC (SEQ ID NO: 1) and / or to a peptide consisting of SEQ ID NO: 769. 48. The polypeptide of any one of embodiments 1-47, wherein the sdAb does not comprise or consist of any one of SEQ ID NO: 138-176 and 641-768. 49. A polynucleotide encoding the polypeptide of any one of embodiments 1-48, optionally wherein the polynucleotide comprises or consists of any one of SEQ ID NOs: 626- 640. 50. A bifunctional polypeptide that promotes proteasome-mediated degradation of at least one target protein, the bifunctional polypeptide comprising: a) a first targeting moiety comprising or consisting of the polypeptide any one of embodiments 1-48, wherein the polypeptide comprises or consists of the anti-Myc sdAb; b) a ubiquitin-proteasome system recruiting domain (URD), c) optionally a first linker peptide, optionally wherein the first linker peptide is positioned between the first targeting moiety and the URD, d) optionally one or more localization peptide sequences, wherein at least one target protein is MYC, optionally c-MYC, and wherein proximity of the bifunctional polypeptide to at the least one target protein through binding of the targeting moiety induces ubiquitination of the at least one target protein via the URD, thereby promoting proteasome-mediated degradation of the at least one target protein. 51. The bifunctional polypeptide of embodiment 50, wherein the URD is derived from at least one E3 ubiquitin ligase. 52. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from a RING family E3 ubiquitin ligase, an H-box family E3 ubiquitin ligase or a viral analogue of an E3 ubiquitin ligase. 53. The bifunctional polypeptide of any one of embodiments 50-52, wherein the URD is selected from: a) the URD derived from a protein which localizes to the cytoplasm, optionally selected from FBXW7 beta and Keap1; b) the URD derived from a protein which localizes to the nucleus, optionally selected from FBXW7 alpha, RNF165, and SPOP, optionally SPOP.2; and c) the URD derived from a protein which localizes to the cytoplasm and the nucleus, optionally selected from beta-TRCP, CHIP, RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E), TRIM21, E6AP, DCAF1 VIF, RNF11, RNF111, RNF115, RNF12, RNF128, RNF149, RNF152, RNF165, RNF182, RNF20, RNF25, RNF4, RNF6, TRIM32, ZNRF1, ZNRF4; d) the URD derived from an E3 ligase selected from the group consisting of NHLRC1, RNF125, RNF165, RNF4, and ZNRF1, optionally NHLRC1, and RNF4 or e) a truncation or fragment of the URD that retains ubiquitin-proteasome recruiting activity, optionally NHLRC1.1, NHLRC1.6, NHLRC1.7, NHLRC1.8, RNF125.2, RNF165.1, RNF4.1, RNF4.2, RNF4.3, RNF4.4, RNF4.5, RNF4.6, RNF4.7, RNF4.8 or ZNRF1.1, optionally NHLRC1.1, or RNF4.1; optionally wherein the protein is an E3 ubiquitin ligase. 54. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from a RING family E3 ubiquitin ligase, a cullin family E3 ubiquitin ligase, a homologous to E6AP carboxyl terminus (HECT) family E3 ubiquitin ligase, and a viral homolog of an E3 ubiquitin ligase. 55. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from an E3 ubiquitin ligase selected from the group consisting of CHIP, DCAF1, E6AP, FBXW7-alpha, FBXW7-beta, Keap1, NHLRC1, RNF4, RNF6, RNF11, RNF12, RNF20, RNF25, RNF111, RNF114, RNF115, RNF125, RNF128, RNF138, RNF149, RNF152, RNF165, RNF166, RNF182, SPOP, beta-TRCP, TRIM21, TRIM32, VIF, ZNRF1, ZNRF4, and CBL-b (Y363E), optionally wherein the portion is selected from the group consisting of CBLb.1, CHIP.1, DCAF1.1, E6AP.1, FBXW7a.1, FBXW7a.2, FBXW7a.3, FBXW7a.4, FBXW7a.5, FBXW7a.6, FBXW7a.7, FBXW7a.8, FBXW7a.9, FBXW7b, FBXW7b.2, FBXW7b.3, FBXW7b.4, Keap1.1, NHLRC1.1, NHLRC1.2, NHLRC1.3, NHLRC1.4, NHLRC1.5, RNF4.1, RNF6.1, RNF6.2, RNF11.1, RNF12.1, RNF12.2, RNF20.1, RNF25.1, RNF111.1, RNF114.1, RNF115.1, RNF125.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF125.7, RNF128.1, RNF138.1, RNF149.1, RNF152.1, RNF165.1, RNF166.1, RNF182.1, RNF182.2, SPOP.1, SPOP.2, SPOP.3, bTRCP.1, TRIM21.1, TRIM21.2, TRIM21.3, TRIM32.1, VIF.1, ZNRF1.1, and ZNRF4.1. 56. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from a monomeric RING family E3 ligase. 57. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from an E3 ligase selected from the group consisting of NHLRC1, RNF11, RNF111, RNF114, RNF115, RNF12, RNF125, RNF128, RNF138, RNF149, RNF152, RNF165, RNF166, RNF182, RNF20, RNF25, RNF4, RNF6, ZNRF1, ZNRF4, and CBL-b (Y363E), or optionally selected from the group consisting of RNF125, NHLRC1, RNF4, RNF6, RNF12, RNF138 and ZNRF1. 58. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is selected from the group consisting of NHLRC1.1, NHLRC1.2, NHLRC1.3, NHLRC1.4, NHLRC1.5, RNF11.1, RNF111.1, RNF114.1, RNF115.1, RNF12.1, RNF12.2, RNF125.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF125.7, RNF128.1, RNF138.1, RNF149.1, RNF152.1, RNF165.1, RNF166.1, RNF182.1, RNF182.2, RNF20.1, RNF25.1, RNF4.1, RNF6.1, RNF6.2, ZNRF1.1, ZNRF4.1, and CBLb.1, optionally selected from the group consisting of NHLRC1.1, NHLRC1.2, NHLRC1.3, NHLRC1.4, NHLRC1.5, RNF125.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF125.7, RNF4.1, RNF6.1, RNF6.2, RNF12.1, RNF12.2, RNF138.1, RNF165.1, and ZNRF1.1. 59. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from a cullin family E3 ligase. 60. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from an E3 ligase selected from the group consisting of DCAF1, beta-TRCP, FBXW7-alpha, FBXW7-beta, Keap1, and SPOP, optionally selected from the group consisting of beta-TRCP, FBXW7-alpha, and FBXW7-beta. 61. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is selected from the group consisting of DCAF1.1, bTRCP.1, FBXW7a.1, FBXW7a.2, FBXW7a.3, FBXW7a.4, FBXW7a.5, FBXW7a.6, FBXW7a.7, FBXW7a.8, FBXW7a.9, FBXW7b, FBXW7b.2, FBXW7b.3, FBXW7b.4, Keap1.1, SPOP.1, SPOP.2, and SPOP.3. 62. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from an E3 ligase NHLRC1, DCAF1, RNF125, RNF165, RNF4, and SPOP, optionally NHLRC1, RNF125, RNF165, RNF4, and SPOP, optionally NHLRC1, RNF125, RNF165, and RNF4, and / or wherein the URD is selected from the group consisting of NHLRC1.1, DCAF1.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF165.1, RNF4.1, SPOP.2, and SPOP.3, optionally NHLRC1.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF165.1, RNF4.1, SPOP.2, and SPOP.3, optionally NHLRC1.1, RNF125.2, RNF165.1, and RNF4.1. 63. The bifunctional polypeptide of any one of embodiments 50-51, wherein the URD is derived from an E3 ligase selected from the group consisting of NHLRC1, RNF125, RNF165, RNF4, and ZNRF1, optionally NHLRC1, RNF125, RNF165, and RNF4, optionally wherein the URD comprises or consists of NHLRC1.1, RNF125.2, RNF165.1, RNF4.1, or ZNRF1.1, optionally wherein the URD comprises or consists of NHLRC1.1, RNF125.2, RNF165.1, or RNF4.1. 64. The bifunctional polypeptide of any one of embodiments 50-63, wherein the number of amino acids in the URD is, is about, or is less than, 80, 75, 70, 65, 60, 65, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or 1%, of the number of amino acids in the wild-type full- length protein from which it is derived, or a range defined by any two of the preceding values, optionally 15-80, 15-50, 25-80, 25-50, 30-60, 1-80, 2-80, 1-70, 2-70, 2-65%, optionally 15- 50%, optionally 2-61%. 65. The bifunctional polypeptide of any one of embodiments 50-64, wherein the URD is less than or equal to 370, 369, 368, 367, 366, 365, 364, 363, 362, 361, 360, 300, 250, 200, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 120, 115, 110, 105, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 25, or 20 amino acids long, or a range defined by any two of the preceding values, optionally 20-370, 20-150, 20-100, 20-80, 30-150, 30-100, 50-150, or 50- 100, optionally 20-100 amino acids long, optionally 40-130 or 44-126. 66. The bifunctional polypeptide of any one of embodiments 50-65, wherein the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 39-113, optionally any one of SEQ ID NO: 54-113, optionally any one of SEQ ID NO: 76, 88, 98, 104 and 111 , optionally any one of SEQ ID NO: 76, 88, 98, and 104, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. 67. The bifunctional polypeptide of any one of embodiments 50-66, further comprising one or more linker peptides, wherein the linker peptide is positioned between one or more of: the targeting moiety and the URD; a localization peptide and the targeting moiety; a localization peptide and the URD; and / or a localization peptide and an epitope tag, optionally an HA tag. 68. The bifunctional polypeptide of any one of embodiments 50-67, comprising a linker peptide positioned between the targeting moiety and the URD. 69. The bifunctional polypeptide of any one of embodiments 50-68, wherein the one or more linker peptides is independently 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 amino acids in length, or a range defined by any two of the preceding values, optionally 0-30, 1-30, 2-30, 0-20, 1-20, 2-20, 0-15, 0-12, 0-10, 1-15, 1-12, 1-10, 2-15, 2-12, 2-10, 3-15, 3-12, or 3-10 amino acids in length, optionally 2-30 amino acids in length. 70. The bifunctional polypeptide any one of embodiments 50-69, wherein the at least one or more linker peptides comprise or consist of glycine and serine. 71. The bifunctional polypeptide any one of embodiments 50-70, wherein the one or more linker peptides comprises or consists of one or more alpha helixes, optionally flanked by one or more glycine and / or a serine residues. 72. The bifunctional polypeptide any one of embodiments 50-71, wherein the one or more linker peptides independently comprise or consist of the amino acid sequence of any one of SEQ ID NO: 345-383 (345-351, GS, and 353-383), optionally SEQ ID N: 347-352 (SEQ ID NO: 347-351 and GS). 73. The bifunctional polypeptide of any one of embodiments 50-72, further comprising one or more localization peptide sequences. 74. The bifunctional polypeptide of embodiment 73, wherein the one or more localization peptide sequences direct the bifunctional polypeptide to a subcellular compartment or compartments, optionally wherein the subcellular compartment is the nucleus and / or the cytoplasm. 75. The bifunctional polypeptide of embodiment 73 or 74, wherein the one or more localization peptide sequences direct the bifunctional polypeptide to a desired subcellular compartment or compartments, optionally wherein the one or more localization peptide sequences are selected or designed to direct the bifunctional polypeptide to a desired subcellular compartment or compartments. 76. The bifunctional polypeptide of any one of embodiments 73-75, wherein the one or more localization peptide sequences comprise or consist of a nuclear localization signal (NLS) peptide and / or a nuclear export signal (NES) peptide, optionally wherein the localization peptide comprises or consists of an amino acid sequence of any one of SEQ ID NO: 114-127. 77. The bifunctional polypeptide of any one of embodiments 73-76, wherein the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the first targeting moiety and / or the URD. 78. The bifunctional polypeptide of embodiment 77, wherein the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the URD. 79. The bifunctional polypeptide of embodiment 78, wherein the endogenous localization peptide sequence is from a URD selected from: a URD derived from a protein which localizes to the cytoplasm, optionally selected from FBXW7 beta and Keap1; a URD derived from a protein which localizes to the nucleus, optionally selected from FBXW7 alpha, RNF165, and SPOP; and a URD derived from a protein which localizes to the cytoplasm and the nucleus, optionally selected from beta-TRCP, CHIP, RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E), TRIM21, E6AP, DCAF1 VIF, RNF11, RNF111, RNF115, RNF12, RNF128, RNF149, RNF152, RNF165, RNF182, RNF20, RNF25, RNF4, RNF6, TRIM32, ZNRF1, ZNRF4. 80. The bifunctional polypeptide of any one of embodiments 73-79, wherein the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the first targeting moiety and / or the URD that is modified, wherein the modification alters the subcellular compartment or compartments to which the bifunctional polypeptide is directed as compared to the native endogenous localization peptide sequence. 81. The bifunctional polypeptide of embodiment 80, wherein the modification comprises or consists of a substitution, truncation or deletion of an endogenous localization peptide sequence. 82. The bifunctional polypeptide of embodiment 80 or 81, wherein: a. the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the cytoplasm; b. the native endogenous localization peptide sequence directs the polypeptide to the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus; c. the native endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to only the cytoplasm; d. the native endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to only the nucleus; e. the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm; or f. the native endogenous localization peptide sequence directs the polypeptide to the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm. 83. The bifunctional polypeptide of embodiment 73-82, wherein the one or more localization peptide sequences comprises or consists of an endogenous localization peptide sequence of the URD that is modified, wherein the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the cytoplasm. 84. The bifunctional polypeptide of any one of embodiments 80-83, wherein the modified endogenous localization peptide sequence comprises or consists of a modified SPOP URD endogenous localization peptide sequence, optionally wherein the URD is SPOP.3. 85. The bifunctional polypeptide of any one of embodiments 73-84, wherein the one or more localization peptide sequences comprise or consist of an exogenous localization peptide sequence. 86. The bifunctional polypeptide of any one of embodiments 73-85, wherein the one or more localization peptide sequences comprise or consist of an NLS peptide that is, or is derived from the NLS of MYC, simian virus 40 (SV40), SPOP, nucleoplasmin, 53BP1, or Hrp1. 87. The bifunctional polypeptide of any one of embodiments 73-86, wherein the one or more localization peptide sequences comprise or consist of an NLS or NES comprising or consisting of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 114-127. 88. The bifunctional polypeptide of any one of embodiments 73-87, wherein the bifunctional polypeptide comprises or consists of two localization peptide sequences, optionally wherein the bifunctional polypeptide comprises or consists of 3, 4, or more localization peptide sequences, optionally wherein the bifunctional polypeptide comprises or consists of 2, 3, 4 or more copies of the same localization sequence in series. 89. The bifunctional polypeptide of any one of embodiments 73-88, comprising one or more localization peptide sequences located at a location selected from the group consisting of: the N-terminus of the bifunctional polypeptide; the C-terminus of the bifunctional polypeptide; internally within the bifunctional polypeptide; as part of the URD, optionally an endogenous portion of the URD; as a part of the first targeting moiety, optionally an endogenous portion of the first targeting moiety; and a combination of any of the foregoing. 90. The bifunctional polypeptide of any one of embodiments 73-89, wherein a first localization peptide sequence is located at the N-terminus of the bifunctional polypeptide and a second localization peptide sequence is located at the C-terminus of the bifunctional polypeptide. 91. The bifunctional polypeptide of any one of embodiments 73-90, further comprising at least one NLS peptide, wherein the at least one NLS peptide is located at the N- terminus of the bifunctional polypeptide, the C-terminus of the bifunctional polypeptide, is part of the URD, optionally an endogenous NLS of the URD, or is part of the first targeting moiety, optionally an endogenous NLS of the first targeting moiety. 92. The bifunctional polypeptide of embodiment 91, wherein a first NLS peptide is located at the N-terminus of the bifunctional polypeptide and a second NLS peptide is located at the C-terminus of the bifunctional polypeptide. 93. The bifunctional polypeptide of any one of embodiments 50-92, wherein the orientation of the targeting moiety relative to the URD is the same orientation as compared to the naturally occurring substrate recognition domain of the protein from which the URD is derived. 94. The bifunctional polypeptide of any one of embodiments 50-93, wherein the orientation of the first targeting moiety relative to the URD is the opposite orientation as compared to the naturally occurring substrate recognition domain of the protein from which the URD is derived. 95. The bifunctional polypeptide of any one of embodiments 50-94, wherein the targeting moiety is N-terminal relative to the URD. 96. The bifunctional polypeptide of any one of embodiments 50-94, wherein the targeting moiety is C-terminal relative to the URD. 97. The bifunctional polypeptide of any one of embodiments 50-96, further comprising an epitope tag, optionally a hemagglutinin (HA) tag, optionally wherein the HA tag comprises or consists of the amino acid sequence of SEQ ID NO: 384, wherein the epitope tag can be used to visualize the dual-specific bifunctional polypeptide. 98. The bifunctional polypeptide of any one of embodiments 50-96, wherein the bifunctional polypeptide does not comprise an epitope tag, optionally a hemagglutinin (HA) tag, optionally wherein the bifunctional polypeptide does not comprise an HA tag comprising or consisting of the amino acid sequence of SEQ ID NO: 384. 99. The bifunctional polypeptide of any one of embodiments 50-98, wherein the bifunctional polypeptide is less than or equal to 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 amino acids long, or a range defined by any two of the preceding values, optionally 50-800, 50-650, 50-500, 50-400, 70-800, 70-650, 70-500, 70-400, 70-300, 70-200, 80-800, 80-650, 80- 500, 80-400, 80-300, or 80-200 amino acids long, optionally 90-550, 150-550, or 80-450 amino acids long. 100. The bifunctional polypeptide of any one of embodiments 50-99, wherein the URD is not derived from CHIP, optionally wherein the URD does not comprise or consist of CHIP.1, optionally wherein the URD does not comprise or consist of SEQ ID NO: 54. 101. A polynucleotide encoding a bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of any one of embodiments 50-100. 102. The bifunctional polypeptide of any one of embodiments 50-100, wherein the at least one target protein comprises MYC, optionally c-MYC. 103. The bifunctional polypeptide of embodiment 102, wherein the bifunctional polypeptide comprises a localization peptide sequence which directs the bifunctional polypeptide to the nucleus of a cell, optionally wherein the localization peptide sequence comprises or consists of the NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin, optionally MYC, SPOP, Hrp1, optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of SPOP, optionally SPNLS.2, MYC, optionally mycNLS, and Hrp1, optionally hrpNLS. 104. The bifunctional polypeptide of embodiment 103, wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127, optionally wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114, 122 and 116. 105. The bifunctional polypeptide of any one of embodiments 102-104, wherein the URD is the URD of NHLRC1, RNF125, RNF165, RNF4, or ZNRF1, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity, optionally wherein the URD comprises or consists of NHLRC1.1, RNF125.2, RNF165.1, RNF4.1, or ZNRF1.1, optionally wherein the URD comprises or consists of NHLRC1.1 RNF125.2, RNF165.1, or RNF4.1. 106. The bifunctional polypeptide of any one of embodiments 102-105, wherein the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76-80, 87- 93, 98, 104 and 111, optionally wherein the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76, 88, 98, 104, and 111, or optionally SEQ ID NOs: 76, 88, 98, and 104. 107. The bifunctional polypeptide of any one of embodiments 102-106, wherein the first targeting moiety comprises or consists of the polypeptide of any one of embodiments 1- 48, wherein the polypeptide comprises or consists of the anti-Myc sdAb. 108. The bifunctional polypeptide of embodiment 107, wherein the first targeting moiety comprises or consists of a VHH domain. 109. The bifunctional polypeptide of any one of embodiments 102-108, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 428-561, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 110. The bifunctional polypeptide of any one of embodiments 102-109, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 27, optionally excluding any one of the SEQ ID NOs listed as having a MYC degradation Grade of D, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 111. The bifunctional polypeptide of any one of embodiments 102-110, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 27 listed as having a MYC degradation Grade of A, and / or MYC degradation Grade of B, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 112. The bifunctional polypeptide of any one of embodiments 102-111, wherein the bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 27 listed as having a MYC degradation Grade of C and / or D, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 113. The bifunctional polypeptide of any one of embodiments 102-112, wherein the URD is not derived from CHIP, optionally wherein the URD does not comprise or consist of CHIP.1, optionally wherein the URD does not comprise or consist of SEQ ID NO: 54. 114. A polynucleotide encoding a bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of any one of embodiments 102-113. 115. The bifunctional polypeptide of any one of embodiments 50-113, wherein the bifunctional polypeptide is a dual-specific bifunctional polypeptide further comprising: a. a second targeting moiety that is capable of binding to at least one second target protein, optionally an intracellular target protein, b. optionally a second linker peptide, wherein the second linker peptide is positioned between the second targeting moiety and the URD or between the first targeting moiety and the second targeting moiety, and wherein proximity of the dual-specific bifunctional polypeptide to at least one target protein through binding of the first targeting moiety and / or the second targeting moiety induces ubiquitination of the at least one target protein via the URD, thereby promoting proteasome- mediated degradation of the at least one target protein. 116. The dual-specific bifunctional polypeptide of embodiment 115, wherein the first targeting moiety binds to and / or is designed to bind a first target protein and the second targeting moiety binds to and / or is designed to bind a second target protein. 117. The dual-specific bifunctional polypeptide of embodiment 115, wherein the first targeting moiety and the second targeting moiety bind to and / or are designed to bind to the same target protein. 118. The dual-specific bifunctional polypeptide of embodiment 117, wherein the first targeting moiety binds to and / or is capable of binding to a first binding site of the target protein and the second targeting moiety binds to and / or is capable of binding to a second binding site of the target protein. 119. The dual-specific bifunctional polypeptide of embodiment 117, wherein the first targeting moiety and second targeting moiety bind to and / or are capable of binding to the same binding site of the target protein, wherein the dual-specific bifunctional polypeptide engages and / or is capable of engaging at least two molecules of the at least one target protein. 120. The dual-specific bifunctional polypeptide of any one of embodiments 115-119, wherein the second targeting moiety is less than or equal to 260, 259, 258, 257, 256, 255, 254, 253, 252, 251, 250, 245, 240, 235, 230, 225, 220, 215, 210, 205, 200, 195, 190, 185, 180, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 122, 121, 120, 119, 118, 117, 116, 115, 114, 113, 112, 110, 109, 108, 107, 106, 105, 104, 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 75, 70, 65, 60, 55, 54, 53, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10 amino acids long, or a range defined by any two of the preceding values, optionally 10-260, 10-200, 10-130, 25-260, 25-200, 25-130, 35-260, 35-200, 35-130, 50-260, 50-200, or 50-130 amino acids long. 121. The dual-specific bifunctional polypeptide of any one of embodiments 115-120, wherein the second targeting moiety comprises or consists of an endogenous binding partner of the at least one target protein, antibody, Fab, F(ab’)2, Fab’, scFv, single domain antibody (sdAb), VH domain, VL domain, VHH, VNAR, diabody, intrabody, DARPin, monobody, affibody, avimer, or any fragment or derivative thereof. 122. The dual-specific bifunctional polypeptide of any one of embodiments 115-121, wherein the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. 123. The dual-specific bifunctional polypeptide of embodiment 122, wherein the second targeting moiety is, or is less than, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 75, 70, 65, 60, 55, 54, 53, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10 amino acids long, or a range defined by any two of the preceding values, optionally 10-100, 10-25, 14-100, 14-25, 30-100, 30-50, 30-45, or 80-100 amino acids long. 124. The dual-specific bifunctional polypeptide of any one of embodiments 115-123, wherein the second targeting moiety comprises or consists of an sdAb, optionally comprising or consisting of either a VH domain or a VL domain of an IgG antibody, or a VHH, VH, or VNAR domain of a heavy chain antibody (HcAb), optionally wherein the sdAb comprises or consists of a VHH or VLdomain. 125. The dual-specific bifunctional polypeptide of embodiment 124, wherein the second targeting moiety is, or is less than, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 122, 121, 120, 119, 118, 117, 116, 115, 114, 113, 112, 110, 109, 108, 107, 106, 105, 104, 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, or 90, amino acids long, or a range defined by any two of the preceding values, optionally 90-150, 90-130, 110-150, 110-130, 110-125, or 114-124 amino acids long. 126. The dual-specific bifunctional polypeptide of embodiment 115-125, wherein the second targeting moiety comprises or consists of an scFv, optionally wherein the targeting moiety is, or is less than, 260, 259, 258, 257, 256, 255, 254, 253, 252, 251, 250, 245, 240, 235, 230, 225, 220, 215, 210, 205, 200, 195, or 190 amino acids long, or a range defined by any two of the preceding values, optionally 190-260, 200-260, or 230-260 amino acids long. 127. The dual-specific bifunctional polypeptide of any of embodiments 115-126, wherein the at least one second target protein is selected from MYC, optionally c-MYC, beta catenin 1 (CTNNB1) and proliferating cell nuclear antigen (PCNA). 128. The dual-specific bifunctional polypeptide of any one of embodiments 115-127, wherein the at least one second target protein is a wild-type and / or a mutant form of the target protein, optionally wherein the targeting moiety preferentially or selectively binds the mutant form of the target protein relative to the wild-type form of the target protein. 129. The dual-specific bifunctional polypeptide of embodiment 128, wherein the mutant form of the target protein is CTNNB1 (SEQ ID NO: 2) comprising one or more mutations selected from: D32Y; D32N; D32V; D32G; S33Y; S33L; S33F; S33C; S33P; G34V; G34E; I35S; H36P; S37C; S37P; S37P and D207G; T41A; T41I; T42_K49del; S45F; and Y670X wherein X indicates termination; S45C; S45F; S45P; S45Y; and S45del. 130. The dual-specific bifunctional polypeptide of any one of embodiments 115-129, wherein the second targeting moiety bind, or bind at least in part, to at least a portion of: a) the DNA binding domain of MYC; b) the armadillo domain of CTNNB1; or c) the p21 binding domain of PCNA. 131. The dual-specific bifunctional polypeptide of any one of embodiments 115-130, wherein the second targeting moiety binds, or binds at least in part, to at least a portion of the target protein selected from the portion consisting of: a) amino acids 54-406 of MYC (SEQ ID NO: 1), b) amino acids 354-406 of MYC (SEQ ID NO: 1), c) amino acids 408-437 of MYC (SEQ ID NO: 1), d) amino acids 410-419 of MYC (SEQ ID NO: 1), e) amino acids 150-663 of CTNNB1 (SEQ ID NO: 2), f) amino acids 15-29 of CTNNB1 (SEQ ID NO: 2), g) amino acids 249-265, 292-306, 379-390, 415-429, 462-470, or 505-519, or any combination thereof, of CTNNB1 (SEQ ID NO: 2), and h) amino acids 38-48, 123-129, or 251-257 or any combination thereof, of PCNA (SEQ ID NO: 3). 132. The dual-specific bifunctional polypeptide of any one of embodiments 115-131, wherein the second targeting moiety is selected from Omomyc, TCF4, TCF4.1, TCF4.2, TCF4.3, TCF4.4, TCF4.5, TCF4.6, TCF4.7, TCF4.8, TCF4.9, TCF4.10, TCF4.11, TCF4.12, TCF4.13, TCF4.14, TCF4.15, TCF4.16, con1, con1.1, con1.2, p21, p21.1, p21.2, p21.3, p21.4, p21.5, p21.6, p21.7, p21.8, p21.9, mycV.0300, mycV.1300, mycV.1500, mycV.3700, mycV.6600, mycV.1516, mycV.1515, mycV.1514, mycV.1513, mycV.1512, mycV.1511, mycV.1510, mycV.1509, mycV.1508, mycV.1507, mycV.1506, mycV.1505, mycV.1504, mycV.1503, mycV.1502, mycV.1501, mycV.0302, mycV.0305, mycV.0306, mycV.0307, mycV.1308, mycV.1517, mycV.1518, mycV.1519, mycV.1520, mycV.1522, mycV.1524, mycV.3706, mycV.3708, mycV.6605, mycV.6608, or a fragment thereof that is capable of binding to the target protein; optionally wherein the second targeting moiety is selected from Omomyc, TCF4, TCF4.1, TCF4.2, TCF4.3, TCF4.4, TCF4.5, TCF4.6, TCF4.7, TCF4.8, TCF4.9, TCF4.10, TCF4.11, TCF4.12, TCF4.13, TCF4.14, TCF4.15, TCF4.16, con1, con1.1, con1.2, p21, p21.1, p21.2, p21.3, p21.4, p21.5, p21.6, p21.7, p21.8, p21.9, mycV.0302, mycV.0305, mycV.0306, mycV.0307, mycV.1308, mycV.1517, mycV.1518, mycV.1519, mycV.1520, mycV.1522, mycV.1524, mycV.3706, mycV.3708, mycV.6605, and mycV.6608; optionally wherein the targeting moiety does not comprise full length or unmodified con1 or p21. 133. The dual-specific bifunctional polypeptide of any one of embodiments 115-132, wherein the second targeting moiety comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 136, 137, 145, 153, 161, 169, 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, 319-344, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761; optionally any one of SEQ ID NO: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, and 319-344. 134. The dual-specific bifunctional polypeptide of any one of embodiments 115-133, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 562-577, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 135. The dual-specific bifunctional polypeptide of any one of embodiments 115-134, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 29 listed as having a degradation Grade of A for at least one of the target proteins, degradation Grade of B for at least one of the target proteins, degradation Grade of C for at least one of the target proteins, and / or degradation Grade of D for at least one of the target proteins, optionally excluding any one of the SEQ ID NOs listed as having a degradation Grade of D for at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 136. The dual-specific bifunctional polypeptide of any one of embodiments 115-135, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 listed as having degradation Grade of A for at least one of the target proteins, and / or degradation Grade of B for at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 137. The dual-specific bifunctional polypeptide of any one of embodiments 115-135, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 listed as having a degradation Combined Grade of A / A or A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 138. The dual-specific bifunctional polypeptide of any one of embodiments 115-135, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 listed as having a degradation Combined Grade of A / B or B / A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 139. The dual-specific bifunctional polypeptide of any one of embodiments 115-135, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 listed as having a degradation Combined Grade of B / B or B, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 140. The dual-specific bifunctional polypeptide of any one of embodiments 115-139, wherein the dual-specific bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 29 listed as having a degradation Grade of C and / or D for at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 141. The dual-specific bifunctional polypeptide of any one of embodiments 115-140, wherein the URD is the URD of NHLRC1, RNF125, RNF165, or RNF4, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity, optionally wherein the URD comprises or consists of NHLRC1.1, RNF125.2, RNF165.1, or RNF4.1. 142. The dual-specific bifunctional polypeptide of any one of embodiments 115-141, wherein the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 76-80, 87-93, 98, and 104, optionally any one of SEQ ID NO: 76, 88, 98, and 104, or a truncation or fragment thereof that retains ubiquitin- proteasome recruiting activity. 143. The dual-specific bifunctional polypeptide of any one of embodiments 115-142, further comprising one or more linker peptides, wherein the linker peptide is positioned between one or more of: the first targeting moiety and the URD; the second targeting moiety and the URD; the first targeting moiety and the second targeting moiety; a localization peptide and the first targeting moiety; a localization peptide and the second targeting moiety; a localization peptide and the URD; and / or a localization peptide and an epitope tag, optionally an HA tag. 144. The dual-specific bifunctional polypeptide of any one of embodiments 115-143, comprising a first linker peptide positioned between the first targeting moiety and the URD or between the second targeting moiety and the URD, and a second linker peptide positioned between the second targeting moiety and the URD or between the first targeting moiety and the second targeting moiety, optionally wherein the first linker peptide is positioned between the first targeting moiety and the URD and the second linker peptide is positioned between the second targeting moiety and the URD. 145. The dual-specific bifunctional polypeptide of any one of embodiments 115-144, wherein the one or more linker peptides is independently1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 amino acids in length, or a range defined by any two of the preceding values, optionally 0-30, 1-30, 2-30, 0-20, 1-20, 2- 20, 0-15, 0-12, 0-10, 1-15, 1-12, 1-10, 2-15, 2-12, 2-10, 3-15, 3-12, or 3-10 amino acids in length, optionally 2-30 amino acids in length. 146. The dual-specific bifunctional polypeptide of any one of embodiments 115-145, wherein the at least one or more linker peptides comprise or consist of glycine and serine. 147. The dual-specific bifunctional polypeptide of any one of embodiments 115-146, wherein the one or more linker peptides comprises or consists of one or more alpha helixes, optionally flanked by one or more glycine and / or a serine residues. 148. The dual-specific bifunctional polypeptide of any one of embodiments 115-147, wherein the one or more linker peptides independently comprise or consist of the amino acid sequence of any one of SEQ ID NO: 345-383 (345-351, GS, and 353-383), optionally SEQ ID NO: 347-352 (SEQ ID NO: 347-351 and GS). 149. The dual-specific bifunctional polypeptide of any one of embodiments 115-148, further comprising one or more localization peptide sequences. 150. The dual-specific bifunctional polypeptide of embodiment 149, wherein the one or more localization peptide sequences direct the dual-specific bifunctional polypeptide to a subcellular compartment or compartments, optionally wherein the subcellular compartment is the nucleus and / or the cytoplasm. 151. The dual-specific bifunctional polypeptide of embodiment 149 or 150, wherein the one or more localization peptide sequences direct the dual-specific bifunctional polypeptide to a desired subcellular compartment or compartments, optionally wherein the one or more localization peptide sequences are selected or designed to direct the dual-specific bifunctional polypeptide to a desired subcellular compartment or compartments. 152. The dual-specific bifunctional polypeptide of any one of embodiments 149-151, wherein the one or more localization peptide sequences comprise or consist of a nuclear localization signal (NLS) peptide and / or a nuclear export signal (NES) peptide, optionally wherein the localization peptide comprises or consists of an amino acid sequence of any one of SEQ ID NO: 114-127. 153. The dual-specific bifunctional polypeptide of any one of embodiments 149-152, wherein the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the first and / or second targeting moiety and / or the URD. 154. The dual-specific bifunctional polypeptide of any one of embodiments 149-153, wherein the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the first and / or second targeting moiety and / or the URD that is modified, wherein the modification alters the subcellular compartment or compartments to which the dual-specific bifunctional polypeptide is directed as compared to the native endogenous localization peptide sequence. 155. The dual-specific bifunctional polypeptide of embodiment 154, wherein the modification comprises or consists of a substitution, truncation or deletion of an endogenous localization peptide sequence. 156. The dual-specific bifunctional polypeptide of embodiment 154 or 155, wherein: a. the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the cytoplasm; b. the native endogenous localization peptide sequence directs the polypeptide to the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus; c. the native endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to only the cytoplasm; d. the native endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to only the nucleus; e. the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm; or f. the native endogenous localization peptide sequence directs the polypeptide to the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm. 157. The dual-specific bifunctional polypeptide of any one of embodiments 149-156, wherein the dual-specific bifunctional polypeptide comprises or consists of two localization peptide sequences, optionally wherein the dual-specific bifunctional polypeptide comprises or consists of 3, 4, or more localization peptide sequences, optionally wherein the wherein the dual-specific bifunctional polypeptide comprises or consists of 2, 3, 4 or more copies of the same localization sequence in series. 158. The dual-specific bifunctional polypeptide of any one of embodiments 149-157, comprising one or more localization peptide sequences located at a location selected from the group consisting of: the N-terminus of the dual-specific bifunctional polypeptide; the C- terminus of the dual-specific bifunctional polypeptide; internally within the dual-specific bifunctional polypeptide; as part of the URD, optionally an endogenous portion of the URD; as a part of the first and / or second targeting moiety, optionally an endogenous portion of the first and / or second targeting moiety; and a combination of any of the foregoing. 159. The dual-specific bifunctional polypeptide of any one of embodiments 149-158, wherein a first localization peptide sequence is located at the N-terminus of the dual-specific bifunctional polypeptide and a second localization peptide sequence is located at the C- terminus of the dual-specific bifunctional polypeptide. 160. The dual-specific bifunctional polypeptide of any one of embodiments 149-159, further comprising at least one NLS peptide, wherein the at least one NLS peptide is located at the N-terminus of the dual-specific bifunctional polypeptide, the C-terminus of the dual- specific bifunctional polypeptide, is part of the URD, optionally an endogenous NLS of the URD, or is part of the first and / or second targeting moiety, optionally an endogenous NLS of the first and / or second targeting moiety. 161. The dual-specific bifunctional polypeptide of embodiment 149-160, wherein a first NLS peptide is located at the N-terminus of the dual-specific bifunctional polypeptide and a second NLS peptide is located at the C-terminus of the dual-specific bifunctional polypeptide. 162. The dual-specific bifunctional polypeptide of any one of embodiments 115-161, wherein the orientation of the first targeting moiety relative to the URD is the same orientation as compared to the naturally occurring substrate recognition domain of the protein from which the URD is derived. 163. The dual-specific bifunctional polypeptide of any one of embodiments 115-161, wherein the orientation of the first targeting moiety relative to the URD is the opposite orientation as compared to the naturally occurring substrate recognition domain of the protein from which the URD is derived. 164. The dual-specific bifunctional polypeptide of any one of embodiments 115-162, wherein the orientation of the second targeting moiety relative to the URD is the same orientation as compared to the naturally occurring substrate recognition domain of the protein from which the URD is derived. 165. The dual-specific bifunctional polypeptide of any one of embodiments 115-162, wherein the orientation of the second targeting moiety relative to the URD is the opposite orientation as compared to the naturally occurring substrate recognition domain of the protein from which the URD is derived. 166. The dual-specific bifunctional polypeptide of any one of embodiments 115-165, wherein the first targeting moiety is N-terminal relative to the URD and the second targeting moiety is C-terminal relative to the URD. 167. The dual-specific bifunctional polypeptide of any one of embodiments 115-166, wherein the first targeting moiety is C-terminal relative to the URD, and the second targeting moiety is N-terminal relative to the URD. 168. The dual-specific bifunctional polypeptide of any one of embodiments 115-165, wherein the first and the second targeting moieties are N-terminal relative to the URD. 169. The dual-specific bifunctional polypeptide of any one of embodiments 115-165, wherein the first and the second targeting moieties are C-terminal relative to the URD. 170. The dual-specific bifunctional polypeptide of any one of embodiments 115-169, further comprising an epitope tag, optionally a hemagglutinin (HA) tag, optionally wherein the HA tag comprises or consists of the amino acid sequence of SEQ ID NO: 384, wherein the epitope tag can be used to visualize the dual-specific bifunctional polypeptide. 171. The dual-specific bifunctional polypeptide of any one of embodiments 115-169, wherein the dual-specific bifunctional polypeptide does not comprise an epitope tag, optionally a hemagglutinin (HA) tag, optionally wherein the dual-specific bifunctional polypeptide does not comprise an HA tag comprising or consisting of the amino acid sequence of SEQ ID NO: 384. 172. The dual-specific bifunctional polypeptide of any one of embodiments 115-171, wherein the dual-specific bifunctional polypeptide is less than or equal to 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950.1000, 1050, 1100, or 1150, amino acids long, or a range defined by any two of the preceding values, optionally 120-400 or 130-370 amino acids long. 173. The dual-specific bifunctional polypeptide of any one of embodiments 115-172, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the peptide of any one of SEQ ID NO: 562-577. 174. The dual-specific bifunctional polypeptide of any one of embodiments 115-173, wherein the at least one second target protein comprises MYC, optionally c-MYC. 175. The dual-specific bifunctional polypeptide of embodiment 174, wherein the second targeting moiety binds, or binds at least in part, to at least a portion of: a.) the DNA binding domain of MYC; b.) amino acids 54-406 of MYC (SEQ ID NO: 1); c.) amino acids 354-406 of MYC (SEQ ID NO: 1); d.) amino acids 408-437 of MYC (SEQ ID NO: 1); and e.) amino acids 410-419 of MYC (SEQ ID NO: 1). 176. The dual-specific bifunctional polypeptide of any one of embodiments 174-175, wherein the bifunctional polypeptide comprises a localization peptide sequence which directs the bifunctional polypeptide to the nucleus of a cell, optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin, optionally MYC, SPOP, Hrp1, optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of MYC, optionally mycNLS, SPOP, optionally spNLS.2, and Hrp1. 177. The dual-specific bifunctional polypeptide of embodiment 176, wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127, optionally wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 122, 114, and 116. 178. The dual-specific bifunctional polypeptide of any one of embodiments 174-177, wherein the URD is the URD of NHLRC1, RNF125, RNF165, and RNF4, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity, optionally NHLRC1.1, RNF125.2, RNF165.1, or RNF4.1. 179. The dual-specific bifunctional polypeptide of any one of embodiment 174-178, wherein the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76-80, 87-93, 98, and 104, optionally any one of SEQ ID NO: 76, 88, 98, and 104. 180. The dual-specific bifunctional polypeptide of any one of embodiments 174-179, wherein the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. 181. The dual-specific bifunctional polypeptide of any one of embodiments 174-180, wherein the second targeting moiety is Omomyc, or a fragment thereof that is capable of binding to the target protein, optionally comprising or consisting of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to SEQ ID NO: 136. 182. The dual-specific bifunctional polypeptide of any one of embodiments 174-179, wherein the second targeting moiety comprises or consists of a sdAb, optionally comprising or consisting of either a VHdomain or a VLdomain of an IgG antibody, or a VHH, VH, or VNARdomain of a heavy chain antibody (HcAb), optionally wherein the sdAb comprises or consists of a VHH domain. 183. The dual-specific bifunctional polypeptide of embodiment 182, wherein the second targeting moiety comprises or consists of a sdAb, optionally a VHH domain, comprising a CDR1 selected from any one of SEQ ID NOs: 139, 147, 163, and 171, a CDR2 selected from any one of SEQ ID NOs: 141, 149, 157, and 165, and a CDR3 selected from any one of SEQ ID NOs: 143, 151, 159, 167, and 175; optionally wherein the combination of CDR1, CDR2, and CDR3 is SEQ ID NOs: 155, 157 and 159; optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 139, 147, 163, 171, 141, 149, 157, 165, 143, 151, 159, 167, and 175. 184. The dual-specific bifunctional polypeptide of embodiment 183, wherein the sdAb, optionally a VHH domain, of the second targeting moiety comprises a VH FR1 selected from any one of SEQ ID NOs: 138 and 170, a VHFR2 of SEQ ID NO: 140, a VHFR3 selected from any one of SEQ ID NOs: 142, 158, and 174, and a VH FR4 selected from any one of SEQ ID NOs: 144 and 152, optionally wherein the combination of FR1, FR2, FR3 and FR4 is SEQ ID NOs: 154, 156, 158, and 160; optionally wherein each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 138, 170, 140, 142, 158, 174, 144, and 152. 185. The dual-specific bifunctional polypeptide of any one of embodiments 182-184, wherein the second targeting moiety comprises or consists of a sdAb, optionally a VHH domain, sequence selected from any one of SEQ ID NOs: 137, 145, 153, 161, 169, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 137, 145, 153, 161, 169, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 137, 145, 153, 161, 169, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761. 186. The dual-specific bifunctional polypeptide of embodiment 182, wherein the second targeting moiety comprises or consists of a sdAb, wherein the sdAb comprises or consists of a VHH domain. 187. The dual-specific bifunctional polypeptide of embodiment 182 or 186, wherein the second targeting moiety comprises or consists of the polypeptide of any one of embodiments 1-48, wherein the polypeptide comprises or consists of the anti-Myc sdAb. 188. The dual-specific bifunctional polypeptide of any one of embodiments 182-187, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 562, 565, 567, and 570-577, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 189. The dual-specific bifunctional polypeptide of any one of embodiments 174-188, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 30, optionally excluding any one of the SEQ ID NOs listed as having a MYC degradation Grade of D, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 190. The dual-specific bifunctional polypeptide of any one of embodiments 174-189, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 30 listed as having a MYC degradation Grade of A, and / or MYC degradation Grade of B, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 191. The dual-specific bifunctional polypeptide of any one of embodiments 174-190, wherein the bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 30 listed as having a MYC degradation Grade of C and / or D, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 192. The dual-specific bifunctional polypeptide of any one of embodiments 174-191, wherein the URD is not derived from CHIP, optionally wherein the URD does not comprise or consist of CHIP.1, optionally wherein the URD does not comprise or consist of SEQ ID NO: 54. 193. A polynucleotide encoding a dual-specific bifunctional polypeptide comprising or consisting of the dual-specific bifunctional polypeptide of any one of embodiments 174-192. 194. The dual-specific bifunctional polypeptide of any one of embodiments 115-173, wherein the at least one second target protein comprises CTNNB1. 195. The dual-specific bifunctional polypeptide of embodiment 194, wherein the CTNNB1 protein is a mutant form of CTNNB1 (SEQ ID NO: 2) comprising one or more mutations selected from: D32Y; D32N; D32V; D32G; S33Y; S33L; S33F; S33C; S33P; G34V; G34E; I35S; H36P; S37C; S37P; S37P and D207G; T41A; T41I; T42_K49del; S45F and Y670X wherein X indicates termination; S45C; S45F; S45P; S45Y; and S45del. 196. The dual-specific bifunctional polypeptide of any one of embodiments 194-195, wherein the bifunctional polypeptide comprises a localization peptide sequence which directs the bifunctional polypeptide to the nucleus of a cell, optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin, optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of MYC, optionally mycNLS, SPOP, optionally spNLS.2, and Hrp1. 197. The dual-specific bifunctional polypeptide of embodiment 195, wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127, optionally wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 122, 114 and 116. 198. The dual-specific bifunctional polypeptide of any one of embodiments 194-197, wherein the URD is the URD of NHLRC1, RNF125, RNF165, and RNF4, optionally NHLRC1, RNF125, and RNF4, or a truncation or fragment thereof that retains ubiquitin- proteasome recruiting activity, optionally NHLRC1.1, RNF125.2, or RNF4.1. 199. The dual-specific bifunctional polypeptide of any one of embodiment 194-198, wherein the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76-80, 87-93, and 104, optionally wherein the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76, 88 and 104. 200. The dual-specific bifunctional polypeptide of any one of embodiments 194-199, wherein the second targeting moiety binds, or binds at least in part, to at least a portion of: a) the armadillo domain of CTNNB1, b) amino acids 150-663 of CTNNB1 (SEQ ID NO: 2), c) amino acids 15-29 of CTNNB1 (SEQ ID NO: 2), and d) amino acids 249-265, 292-306, 379-390, 415-429, 462-470, or 505-519, or any combination thereof, of CTNNB1 (SEQ ID NO: 2). 201. The dual-specific bifunctional polypeptide of any one of embodiments 194-200, wherein the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. 202. The dual-specific bifunctional polypeptide of any one of embodiments 194-201, wherein the second targeting moiety is TCF4.1, TCF4.2, TCF4.3, TCF4.4, TCF4.5, TCF4.6, TCF4.7, TCF4.8, TCF4.9, TCF4.10, TCF4.11, TCF4.12, TCF4.13, TCF4.14, TCF4.15, or TCF4.16, or a fragment thereof that is capable of binding to the target protein, optionally TCF4.6. 203. The dual-specific bifunctional polypeptide of any one of embodiments 194-202, wherein the second targeting moiety comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 319-333, optionally SEQ ID NO: 330. 204. The dual-specific bifunctional polypeptide of any one of embodiments 194-203, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 563, 564, 566, 568, and 569, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 205. The dual-specific bifunctional polypeptide of any one of embodiments 194-204, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 31, optionally excluding any one of the SEQ ID NOs listed as having a degradation Grade of D for at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 206. The dual-specific bifunctional polypeptide of any one of embodiments 194-205, wherein the bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 31 listed as having a degradation Grade of A for at least one target protein, and / or a degradation Grade of B for at least one target protein, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 207. The dual-specific bifunctional polypeptide of any one of embodiments 194-205, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 31 listed as having a degradation Combined Grade of A / A or A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 208. The dual-specific bifunctional polypeptide of any one of embodiments 194-205, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 31 listed as having a degradation Combined Grade of A / B or B / A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 209. The dual-specific bifunctional polypeptide of any one of embodiments 194-205, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 31 listed as having a degradation Combined Grade of B / B or B, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 210. The dual-specific bifunctional polypeptide of any one of embodiments 194-209, wherein the bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 31 listed as having a degradation Grade of C and / or D for at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 211. The bifunctional polypeptide of any one of embodiments 194-210, wherein the URD is not derived from beta-TRCP, optionally wherein the URD does not comprise or consist of bTRCP.1, optionally wherein the URD does not comprise or consist of SEQ ID NOs: 57. 212. A polynucleotide encoding a bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of any one of embodiments 194-211. 213. The dual-specific bifunctional polypeptide of any one of embodiments 115-173, wherein the at least one target protein comprises PCNA. 214. The dual-specific bifunctional polypeptide of embodiment 213, wherein the bifunctional polypeptide comprises a localization peptide sequence which directs the bifunctional polypeptide to the nucleus of a cell, optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin, optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of MYC, optionally mcyNLS and / or 3xmycNLS, SPOP, Hrp1, SV40; optionally wherein the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of MYC, optionally mcyNLS, and SPOP, optionally spNLS.2. 215. The dual-specific bifunctional polypeptide of embodiment 214, wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127, optionally wherein the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 115-116, and 118-122. 216. The dual-specific bifunctional polypeptide of any one of embodiments 213-215, wherein the URD is the of NHLRC1, RNF125, RNF165, and RNF4, optionally NHLRC1, RNF125, and RNF4, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity, optionally NHLRC1.1, RNF125.2, or RNF4.1. 217. The dual-specific bifunctional polypeptide of any one of embodiments 213-216, wherein the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76-80, 87-93, and 104, optionally wherein the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76, 88 and 104. 218. The dual-specific bifunctional polypeptide of any one of embodiments 213-217, wherein the second targeting moiety binds, or binds at least in part, to at least a portion of amino acids 38-48, 123-129, or 251-257 or any combination thereof, of PCNA (SEQ ID NO: 3): 219. The dual-specific bifunctional polypeptide of any one of embodiments 213-218, wherein the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. 220. The dual-specific bifunctional polypeptide of any one of embodiments 213-219, wherein the second targeting moiety comprises or consists of con1.1, con1.2, p21.1, p21.2, p21.3, p21.4, p21.5, p21.6, p21.7, p21.8, p21.9, or a fragment thereof that is capable of binding to the target protein. 221. The dual-specific bifunctional polypeptide of any one of embodiment 213-220, wherein the first and / or second targeting moiety comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 334-344. 222. The dual-specific bifunctional polypeptide of any one of embodiments 213- 221, wherein the URD is not derived from SPOP, optionally wherein the URD does not comprise or consist of SPOP.1, SPOP.2, or SPOP.3, optionally wherein the URD does not comprise or consist of a sequence selected from any one of SEQ ID NOs: 72-74. 223. A polynucleotide encoding a dual-specific bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of any one of embodiments 213-222. 224. The dual-specific bifunctional polypeptide of embodiment 115, wherein the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 562-577, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 225. A polypeptide comprising or consisting of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, and 385-577, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). 226. A polynucleotide encoding for the polypeptide of embodiment 225. 227. The polynucleotide of any one of embodiments 49, 101, 114, 193, 212, or 226, wherein the polynucleotide is a DNA or an RNA, optionally an mRNA or a circular RNA, optionally wherein the RNA, mRNA or circular RNA comprises one or more modified nucleosides, optionally wherein up to 100% of the nucleotides comprising uracil are replaced with pseudouridine and / or N1-methylpseudouridine. 228. The polynucleotide of any one of embodiments 226-227, wherein the polynucleotide is packaged in a lipid nanoparticle, a polymeric nanoparticle, an extracellular vesicle, optionally an exosome, or a viral vector, optionally a replicating viral vector or a non- replicating viral vector, optionally an adenovirus, adeno-associated virus, lentivirus, or retrovirus vector. 229. A pharmaceutical composition comprising the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, or polynucleotide of any one of embodiments 1-228 and one or more pharmaceutically acceptable excipients, carriers, or diluents. 230. The pharmaceutical composition embodiment 229, wherein the composition is formulated for intravenous, intraperitoneal, intra-arterial, subcutaneous, intramuscular, intrathecal, intratumoral, inhalation, or intracranial administration. 231. The polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of embodiments 1-230 for use in the treatment of a cancer in a patient in need thereof. 232. The polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of embodiments 1-231 for use in the manufacture of a medicament, optionally for the treatment of cancer. 233. A method of treating a subject comprising administering the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of embodiments 1-232 to a subject in need thereof, optionally wherein the subject has a cancer. 234. A method of reducing the amount of a target protein in a cell comprising contacting the cell with the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of embodiments 1-232, optionally wherein the target protein is selected from MYC, (optionally c-MYC), CTNNB1, and / or PCNA. 235. The method of embodiment 233 or 234, wherein said cell is in a subject, and said contacting comprises administering the polypeptide comprising or consisting of the anti- Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of embodiments 1-232 to the subject, optionally wherein the subject has cancer. 236. The method of embodiment 235, wherein the administering is intravenous, intraperitoneal, intra-arterial, subcutaneous, intramuscular, intrathecal, intratumoral, inhalation, or intracranial administration. 237. The method of any one of embodiments 234 or 235, wherein the cell is ex vivo, and said contacting comprises contacting the polypeptide comprising or consisting of the anti- Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of embodiments 1-232 to the cell ex vivo, optionally in an adoptive cell therapy. 238. The method of embodiment 237, further comprising administering the cell to a subject after the contacting step, optionally wherein the subject is also the source of the cell. 239. The polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, pharmaceutical composition or method of any one of embodiments 1-238, wherein the polypeptide, bifunctional polypeptide, or dual-specific bifunctional polypeptide promotes proteasome-mediated degradation of the target protein when measured in one or more assays described in the Exemplary Assays for assessing proteasomal-mediated degradation, for example, by HiBiT tag assay and / or Western blot, optionally wherein the proteasome-mediated degradation is inhibited when the cells comprising the target protein and the dual-specific bifunctional polypeptide are treated with a proteasome inhibitor. 240. The polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, pharmaceutical composition or method of embodiment 239, wherein treatment of the cells comprising the target protein and the polypeptide, bifunctional polypeptide, or dual-specific bifunctional polypeptide with a proteasome inhibitor reduces the amount of degradation of the target protein by at least 50%, 60%, 70%, 80%, 90%, 95% or 100% as compared to cells not treated with the proteasome inhibitor. 241. The bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, pharmaceutical composition, or method of any one of embodiments 50-240, wherein the polypeptide, bifunctional polypeptide, or dual-specific bifunctional polypeptide does not comprise a URD derived from CHIP, SPOP, TRIM21 or beta-TRCP. 242. A compound comprising the polypeptide of any one of embodiments 1-48, the polypeptide comprising or consisting of the anti-Myc sdAb, and a therapeutic compound and / or drug and / or detectable label conjugated to the polypeptide. 243. Any one of the preceding embodiments, wherein the conservative substitution is a conservative substitution from one of the following eight groups, wherein each group contains amino acids that are conservative substitutions for one another: 1) Alanine (A), Glycine (G); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W); 7) Serine (S), Threonine (T); and 8) Cysteine (C), Methionine (M). BRIEF DESCRIPTION OF THE DRAWINGS In addition to the features described above, additional features and variations will be readily apparent from the following descriptions of the drawings and exemplary embodiments. It is to be understood that these drawings depict typical embodiments and are not intended to be limiting in scope. FIGS. 1A, 1B and 1C depict embodiments of a schematic describing proteasome- mediated degradation of a target protein using a bifunctional (FIG. 1A) or dual-specific bifunctional polypeptide (FIGS. 1B and 1C), which comprises a first and optionally a second targeting domain specific for a first and optionally second target protein and a URD comprising an E3 ligase or component, fragment, or truncation thereof that recruits the ubiquitination complex to ubiquitinate one (FIG. 1A) or both (FIGS. 1B and 1C) of the target protein(s) for proteasomal degradation. FIG. 1B depicts an embodiment of a “contralateral” configuration of a dual-specific bifunctional polypeptide in which the first and second targeting domains are located on either side of the URD. FIG. 1C depicts and embodiment of a “tandem” configuration of a dual-specific functional polypeptide in which the first and second targeting domains are located on the same side (both on the N-terminal side or both on the C-terminal side of the URD). FIGS. 2A, 2B and 2C depict embodiments of a schematic for different ordering combinations of the components that comprise the bifunctional or dual-specific bifunctional polypeptides of some embodiments disclosed herein. FIG.2A depicts embodiments of a mono- specific bifunctional polypeptide comprising a single targeting moiety that is capable of binding to at least one target protein (e.g., Myc). FIG. 2B depicts embodiments of a “contralateral” configuration in which the dual-specific bifunctional polypeptides comprise a first targeting moiety (target binding domain) (N-TBD or C-TBD) that is capable of binding to at least one target protein (e.g., Myc); a second targeting moiety (C-TBD or N-TBD) that is capable of binding to at least one target protein (e.g. Myc or a different target protein); and a URD. FIG. 2C depicts embodiments of a “tandem” configuration in which the dual-specific bifunctional polypeptide is in a “tandem” configuration in which the first and second target binding domains are both on the same side of the URD, i.e., both are on the C-terminal side of the URD, or both are on the N-terminal side of the URD. In some embodiments the bifunctional or dual-specific bifunctional polypeptide further comprises one or more linker peptides. In some embodiments when in a “contralateral” configuration the dual-specific bifunctional polypeptide further comprises a first linker peptide (N-linker or C-linker), wherein the first linker peptide is positioned between the first targeting moiety and the URD; and / or a second linker peptide (C-linker or N-linker), wherein the second linker peptide is positioned between the second targeting moiety and the URD. In some embodiments, there is no linker between the first and / or second targeting moiety and the URD. In some embodiments when a “tandem” configuration is used (see, e.g., FIG. 2C), a linker peptide (a first or a second linker peptide) is positioned between the two target binding domains, and / or a target binding domain and the URD. In some embodiments of the tandem configuration one or both of the linkers is not present (not shown). The linker(s), if present, may provide flexibility in positioning between the URD and target binding moiety. In some embodiments, the bifunctional or dual- specific bifunctional polypeptides may further comprise a localization sequence, (e.g., a nuclear localization signal (NLS)), which may be at the N-terminus, C-terminus, or both the N-terminus and C-terminus, or internally (not shown) within the bifunctional polypeptide (e.g., if the URD and / or target binder comprises an NLS within its sequence), if the target protein localizes to the nucleus of a cell. In some embodiments, the localization sequence(s) (e.g., N- NLS, and / or C-NLS) may be separated from other components by a linker sequence (not shown). FIG. 3 depicts an embodiment of subcellular localization of SPOP variant URD mono-specific bifunctional polypeptides to the nucleus and the cytoplasm. FIG. 4 depicts an embodiment of subcellular localization of NHLRC1 containing mono-specific bifunctional polypeptides with and without an exogenous NLS sequence. FIG.5 depicts an embodiment of subcellular localization of VL12.3 containing mono- specific bifunctional polypeptides with URDs containing endogenous NLS or NES signals. FIG.6 is a table disclosing a summary of an embodiment of an experiment examining expression of various exemplary dual-specific bifunctional polypeptides. Provided is a description of elements listed in a N- to C-terminal direction, a summary of the observed subcellular localization of HA staining and the respective SEQ ID NOs. FIGS. 7A-7C depict an embodiment of HA staining of the dual-specific bifunctional polypeptides disclosed in FIG. 6. FIG. 8 depicts an embodiment of various exemplary bifunctional or dual-specific bifunctional polypeptides listing the target proteins (“Targets”), description of elements listed in a N- to C-terminal direction, and respective SEQ ID NOs. DETAILED DESCRIPTION OF THE DISCLOSURE Antibodies targeting Myc such as 9E10 are known in the art. However, antibodies or binding portions thereof which require a disulfide bond to maintain proper folding of the polypeptide for target binding typically do not function in the highly reducing conditions of the intracellular environment. Therefore, the anti-Myc sdAbs disclosed herein, are designed to function in the intracellular environment. This allows these anti-Myc sdAbs to be expressed intracellularly and utilized as Myc-binding moieties on their own, or as portions of other compounds or polypeptides (e.g., antibody-drug conjugates, detectably labeled probes, diabodies, etc.), for example the bifunctional polypeptides disclosed herein. While these anti- Myc sdAbs have the advantage of functioning in highly reducing environments such as the intracellular environment, they are not limited to use in the intracellular environment. In some embodiments, the anti-Myc sdAbs disclosed herein are part of a bifunctional polypeptide that uses the ubiquitin-proteasome system to degrade Myc and optionally other target protein(s). The ubiquitin-proteasome system is the major and essential mechanism by which eukaryotic cells regulate protein abundance and clear misfolded or damaged proteins through proteolytic degradation. This regulation is vital for many cellular functions, such as regulating the cell cycle and gene expression. Proteins are marked for degradation and recognized by the proteasomal complex when they are polyubiquitinated at lysine residues. This polyubiquitination is mediated by recognition of the target proteins by an E3 ubiquitin ligase, which catalyzes the transfer of a ubiquitin subunit from an E2 ubiquitin-conjugating enzyme to the protein target. As ubiquitin also contains ubiquitination sites, the protein target can be polyubiquitinated, thereby marking it for degradation by the proteasome. It is estimated that there are over 600 unique E3 ubiquitin ligases encoded by the human genome, each having varying specificities to target proteins. Therefore, each E3 ubiquitin ligase generally comprises a substrate recognition domain specific for one or more targets and a ubiquitin-proteasome system recruiting domain (URD) that binds to an E2 ubiquitin-conjugating enzyme to enable ubiquitination of the target. As disclosed herein, the ubiquitin-proteasome system may be exploited for the directed degradation of desired protein targets such a Myc. For example, many diseases are associated with the abnormal function and / or expression of certain proteins (e.g., cancer caused by dysfunctional expression or localization of oncogenes). Degradation of said proteins can have a therapeutic effect in treating associated diseases, and the ubiquitin-proteasome system offers a naturally occurring process for effecting said degradation. Furthermore, degradation of disease-associated proteins may be more effective than inhibition of the protein, for example, using a small molecule or antibody composition, as in these cases, the protein is still present within the cell and may perform various biological functions at interfaces other than the inhibited domain, for example scaffolding functions, or contribute to pathology as a result of accumulation, aggregation or mislocalization. Several groups have reported on the structure and preclinical activity of various macromolecule degrader formats, including fusion proteins comprising a full-length or truncated E3 ligase and macromolecular targeting constructs. However, general design principles for such macromolecule degraders are not yet well established, comparatively few of the hundreds of naturally occurring E3 ligases have been explored in this context, and degradation of intracellular targets using macromolecule degraders has been demonstrated for only a limited number of target proteins. Furthermore, there is little precedent for the optimization of drug-like properties for such molecules, and none have yet advanced to the stage of clinical testing. Examples of previous macromolecule degraders have been explored in: Wang et al., “The state of the art of PROTAC technologies for drug discovery,” Eur J. Med. Chem. (2022) 235:114290; Lim et al., “bioPROTACs as versatile modulators of intracellular therapeutic targets including proliferating cell nuclear antigen (PCNA),” PNAS (2020) 117(11):5791-5800; Hatakeyama et al. “Targeted destruction of c-Myc by an engineered ubiquitin ligase suppresses cell transformation and tumor formation,” Cancer Res. (2005) 65(17):7874-9; Portnoff et al. “Ubiquibodies, synthetic E3 ubiquitin ligases endowed with unnatural substrate specificity for targeted protein silencing,” J. Biol. Chem. (2014) 289(11):7844-55; Liao et al. “A PROTAC peptide induces durable β-catenin degradation and suppresses Wnt-dependent intestinal cancer,” Cell Discov. (2020) 6:35; Liu et al. Targeted degradation of b-catenin by chimeric F-box fusion proteins. Biochem. and Biophys. Res. Comm. (2004) 313:1023-1029; Cong et al., “A protein knockdown strategy to study the function of β-catenin in tumorigenesis,” BMC Molecular Bio. (2003) 4:10; and Shu et al. “Eradication of pathogenic β-catenin by Skp1 / Cullin / F box ubiquitination machinery,” PNAS (2003) 100(22)12729-12734; each of which is hereby expressly incorporated by reference in its entirety. Localization of degraders to the correct subcellular compartment may be important for the ability to degrade a target protein, e.g., if the target is localized to the nucleus, or if degradation of target protein only in the nucleus but not cytoplasm is desired. It is noteworthy that apparently none of these references address, or even consider, this potentially important aspect of degrader design. Further, it is noted that none of these degrader formats include dual- specific bifunctional polypeptides as disclosed herein. Accordingly, provided herein are several anti-Myc sdAbs, and polypeptides comprising or consisting thereof. Also disclosed are bifunctional, optionally dual-specific, polypeptides that promote proteasome-mediated degradation of a target protein, and uses thereof, such as for the treatment of a disease. These bifunctional polypeptides generally comprise a first component that is able to bind to a first target protein with specificity (e.g., an anti-Myc sdAb), a second component that is able to recruit a ubiquitination complex to mark the target protein for proteasomal degradation by ubiquitination, and optionally, a third component that is able to bind to a second target protein with specificity (e.g., Myc or a second target protein). An exemplary schematic for the function of a mono-specific bifunctional polypeptide comprising a single targeting moiety as disclosed herein is depicted in FIG. 1A. An exemplary schematic for the function of dual-specific bifunctional polypeptides disclosed herein may be seen in FIG. 1B (contralateral) and 1C (tandem). FIG. 2A, 2B and 2C depict some non-limiting embodiments of mono-specific (FIG. 2A) dual-specific (FIG. 2B and 2C) bifunctional polypeptides with various combinations of targeting moieties and URD, and optionally localization sequences (e.g., NLS) and linkers (the depiction is in the conventional N-terminal to C-terminal (left to right) orientation). In some embodiments, the first and second targeting domains are on either side of the URD (see, e.g., FIG 2B) in a “contralateral” configuration. In some embodiments the first and second target binding domains are on the same side of the URD (both on the N-terminal side, or both on the C-terminal side) (see, e.g., FIG. 2C) in a “tandem” configuration. In some embodiments shown in FIG. 2A, 2B, or 2C a localization sequence (e.g., NLS) is present at both the N- and C-terminal ends. In some embodiments not shown each of the localization signals (e.g., NLS) shown can represent one, two, three or more copies of the same or a different NLS sequence. In some embodiments, the localization sequence(s) (e.g., N-NLS, and / or C-NLS) may be separated from other components by a linker sequence (not shown). In some embodiments provided herein are mono- or dual-specific bifunctional polypeptides which are engineered (e.g., by modification of an endogenous localization peptide sequence, by adding localization peptide sequences, and / or by selecting a component which has an endogenous localization sequence) to direct the bifunctional polypeptide to a particular subcellular compartment, e.g., the cytoplasm, the nucleus, or both. Further, in some embodiments provided herein are polypeptides comprising or consisting of a portion derived from a an E3 ubiquitin ligase or viral homolog thereof. In some embodiments, the portion has ubiquitin-proteasome recruiting activity and may be designated as a ubiquitin recruiting domain (URD). In some embodiments provided herein are dual-specific bifunctional polypeptides comprising these portions. Anti-Myc Single Domain Antibodies (sdAb) Disclosed herein are polypeptides comprising or consisting of an anti-Myc sdAb. In some embodiments, the anti-Myc sdAb, comprises or consists of a VHdomain of an IgG antibody, or a VHH, or VHdomain of a heavy chain antibody (HcAb). Sequences of exemplary anti-Myc sdAbs are shown in Table 1A. Table 1A: Exemplary anti-Myc sdAb Sequences In the above table CDR refers to a complementarity-determining region of the sdAb, and FR refers to a framework region of the sdAb, while “full” is the entire anti-Myc sdAb sequence. Note that not every sequence in the above table is unique, as some exemplary anti- Myc sdAbs share one or more sequences. For example, all of the FR2 sequences are identical even though a separate SEQ ID NO is provided for each FR2 sequence. Table 1B below provides a list of SEQ ID NOs which have identical sequences. Table 1B: List of SEQ ID NOs having identical sequences The above exemplary anti-Myc sdAbs are affinity optimized antibodies of five parental anti-Myc sdAbs, the sequences of which are provided in Table 2 below. Table 2: Parental anti-Myc sdAb sequences The exemplary anti-Myc sdAbs disclosed in Table 1 have improved affinity for the target protein c-Myc as compared to the parental anti-Myc sdAb from which they are derived as evidenced by the Kd values calculated for each. The Kd values for the exemplary anti-Myc sdAbs and the parental anti-Myc sdAbs are provided in Table 3. “Octet sdAb Kd Human Myc Peptide Monovalent (M)” refers to the affinity of the anti-Myc sdAb against human c-Myc antigen peptide as described in more detail in Example 4. “Octet sdAb Kd Human Myc-Fc Monovalent (M)” refers to the affinity of the anti-Myc sdAb against human c-Myc antigen-Fc fusion as described in more detail in Example 4. Table 3: Kd Values of exemplary and parental anti-Myc sdAb By aligning all of the parental and exemplary anti-Myc sdAb sequences, the following exemplary consensus sequences were prepared. Tables 4-9 are alignments of each of CDR1, CDR2, CDR3, FR1, FR3, and FR4 of all of the exemplary and parental anti-Myc sdAbs listed in Tables 1A and 2 above, with the resulting consensus sequences for each. The sequence of FR2 was identical across all anti-Myc sdAbs and therefore no table is provided for the FR2 consensus sequence. Table 4: Consensus CDR1 Table 5: Consensus CDR2 with parental Table 6: Consensus CDR3 Table 7: Consensus FR1 Table 8: Consensus FR3 Table 9: Consensus FR4 Similar exemplary consensus sequences were prepared for each of CDR1-3 for each family of anti-Myc sdAbs (mycV.0300, mycV.1300, mycV.1500, mycV.3700, and mycV.6600) using the parental anti-Myc sdAb and exemplary variant anti-Myc sdAbs derived from the parental sequences. Because each of the CDR3 sequences for the mycV.3700 family were identical, and each of the CDR3 sequences for the mycV.6600 family were identical, no table is presented for the CDR3 consensus sequence for either family. Tables 10-22 provide the resulting consensus sequences. Table 10: mycV.0300 Consensus CDR1 Table 11: mycV.0300 Consensus CDR2 Table 12: mycV.0300 Consensus CDR3 Table 13: mycV.1300 Consensus CDR1 Table 14: mycV.1300 Consensus CDR2 Table 15: mycV.1300 Consensus CDR3 Table 16: mycV.1500 Consensus CDR1 Table 17: mycV.1500 Consensus CDR2 Table 18: mycV.1500 Consensus CDR3 Table 19: mycV.3700 Consensus CDR1 Table 20: mycV.3700 Consensus CDR2 Table 21: mycV.6600 Consensus CDR1 Table 22: mycV.6600 Consensus CDR2 In some embodiments, the CDR, FR, full and consensus sequences provided in the preceding tables can be used to define polypeptides comprising or consisting of an anti-Myc sdAb. In some embodiments, a consensus sequence has variable residues having one of the amino acid specified, or optionally “a conservative substitution of any of the foregoing.” For example, variable residues X1X2X3X4 and X5 in SEQ ID NO: 317 as shown in Table 22, comprise the amino acid specified for the XXresidues as shown in the table, or optionally a conservative substitution of any of the amino acids specified for that XX residue. For example, Table 22 specifies that X1 in SEQ ID NO: 317 may comprise G or A, and thus in some embodiments also contemplated is a conservative substitution of G or a conservative substitution for A. Similarly, X2may be S or D, and optionally in some embodiments a conservative substitution for S, or a conservative substitution for D. The same applies for each of X3, X4 and X5 in SEQ ID NO: 317, as well as the other consensus sequences provided in the preceding tables and elsewhere herein. In some embodiments, the following eight groups each contain amino acids that are conservative substitutions for one another: 1) Alanine (A), Glycine (G); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W); 7) Serine (S), Threonine (T); and 8) Cysteine (C), Methionine (M) (see, for example, Creighton, T. E., “Proteins - Structures and Molecular Properties,” W. H. Freeman & Co. Ltd., 1984). Exemplary Anti-Myc Single Domain Antibodies (sdAb) Some embodiments disclosed herein are a polypeptide comprising or consisting of an anti-Myc sdAb. In some embodiments, including any of the foregoing, the anti-Myc sdAb comprises or consists of a VHdomain of an IgG antibody, or a VHH, or VHdomain of a heavy chain antibody (HcAb), wherein the VH or VHH domain comprises a VH CDR3 comprising or consisting of any one of SEQ ID NOs: 179, 195, 211, 219, 251, 267 or 283. In some embodiments, the VH CDR3 sequence comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 179, 195, 211, 219, 251, 267 and 283. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AX1X2X3X4X5X6X7X8X9X10X11X12EX13DY (SEQ ID NO: 299), wherein X1is A, H, Y, I, or T; X2is L or I; X3is G, D or P; X4is D, Q, G or E; X5is Y, E or I; X6is G, L or S; X7is D,T, S or G; X8 is A, G, F, or no amino acid; X9 is I, G, or no amino acid; X10 is D, G, T or L; X11 is Y, A, F or G; X12 is S, D or N; and X13 is A, H, G or Y; or optionally a conservative substitution of any of the foregoing; wherein the CDR3 does not comprise or consist of any one of SEQ ID NOs: 143, 151, 159, 167, or 175. In some embodiments, including any of the foregoing, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 177, 185, 201, 209, 217, 225, 233, 241, 249, 257, 265, 273, 281, 289; a CDR2 comprising or consisting of any one of SEQ ID NOs: 178, 186, 194, 202, 210, 218, 226, 234, 242, 250, 266, 274, 282 or 290; and a CDR3 comprising or consisting of any one of SEQ ID Nos: 179, 195, 211, 219, 251, 267 or 283. In some embodiments, the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a) SEQ ID NOs: 177, 178, and 179; b) SEQ ID NOs: 185, 186, and 187; c) SEQ ID NOs: 177, 194, and 195; d) SEQ ID NOs: 201, 202, and 179; e) SEQ ID NOs: 209, 210, and 211; f)SEQ ID NOs: 217, 218, and 219; g) SEQ ID NOs: 225, 226, and 219; h) SEQ ID NOs: 233, 234, and 219; i) SEQ ID NOs: 241, 242, and 219; j) SEQ ID NOs: 249, 250, and 251; k) SEQ ID NOs: 257, 218, and 219; l) SEQ ID NOs: 265, 266, and 267; m) SEQ ID NOs: 273, 274, and 267; n) SEQ ID NOs: 281, 282, and 283; and o) SEQ ID NOs: 289, 290, and 283. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 177-179, 185-186, 194-195, 201- 202, 209-211, 217-219, 225-226, 233-234, 241-242, 249-251, 257, 265-267, 273-274, 281- 283, or 289-290. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, including any of the foregoing, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of FX1FX2X3X4X5MX6 (SEQ ID NO: 297), wherein X1 is T or D; X2 is A, S, E, G or D; X3 is D, T, G, E, V or S; X4 is T, M, Q, A, H, Y, V or N; X5is D, P or A; and X6is G or S; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of AIX1X2X3X4X5X6X7YYADSVX8G (SEQ ID NO: 298), wherein X1 is S or no amino acid; X2 is G, A, P, R or S; X3 is S, D, T or G; X4is G, A, S, or E; X5is G, D, E, A or S; X6is N, V, A, S, E, T, D or H; X7is T or A; and X8is K or R; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of AX1X2X3X4X5X6X7X8X9X10X11X12EX13DY (SEQ ID NO: 299), wherein X1is A, H, Y, I, or T; X2is L or I; X3is G, D or P; X4is D, Q, G or E; X5is Y, E or I; X6is G, L or S; X7is D,T, S or G; X8is A, G, F, or no amino acid; X9is I, G, or no amino acid; X10 is D, G, T or L; X11 is Y, A, F or G; X12 is S, D or N; and X13 is A, H, G or Y; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2, and CDR3 is not one of the following combinations: a.) CDR1, CDR2 and CDR3 of mycV.0300 (SEQ ID NOs: 139, 141 and 143); b.) CDR1, CDR2 and CDR3 of mycV.1300 (SEQ ID NOs: 147, 149 and 151); c.) CDR1, CDR2 and CDR3 of mycV.1500 SEQ ID NOs: (155, 157 and 159); d.) CDR1, CDR2 and CDR3 of mycV.3700 SEQ ID NOs: (163, 165 and 167); and e.) CDR1, CDR2 and CDR3 of mycV.6600 SEQ ID NOs: (171, 173 and 175). Note that in the sequence listing submitted herewith, SEQ ID NO: 297 is blank, as sequence listing rules do not permit an amino acid sequence with fewer than four “specifically defined” amino acids, and SEQ ID NO: 297, (FX1FX2X3X4X5MX6) has only three “specifically defined” amino acids at positions 1, 3 and 8. In SEQ ID NO: 297, X6 is either G or S (see Table 4 above). For purposes of the sequence listing, SEQ ID NO: 297 is represented by two sequences, SEQ ID NO: 772 (FX1FX2X3X4X5MG) and SEQ ID NO: 773 (FX1FX2X3X4X5MS), which represent the sequences wherein X6 is specified as G or S, respectively, with X1, X2, X3, X4, and X5 defined as in SEQ ID NO: 297 (see Table 4 above). Therefore, SEQ ID NO: 297 is the same as the combined sequences of SEQ ID NOs 772 and 773, and the combination of SEQ ID NOs: 772 and 773 can replace SEQ ID NO: 297, optionally wherein the G or S at the position of X6 of SEQ ID NO: 772 and 772 is substituted with a conservative substitution of G or S. In some embodiments, including any of the foregoing, the sdAb, optionally a VHH domain, comprises a VHFR1 comprising or consisting of any one of SEQ ID NOs: 180, 188, 212, 228 or 284, a VH FR2 comprising or consisting of SEQ ID NO: 181, a VH FR3 comprising or consisting of any one of SEQ ID NOs: 182, 190, 278 or 286, and a VHFR4 comprising or consisting of any one of SEQ ID NOs: 183 or 215, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a.) SEQ ID NOs: 180, 181, 182, and 183; b.) SEQ ID NOs: 188, 181, 182, and 183; c.) SEQ ID NOs: 212, 181, 182, and 215; d.) SEQ ID NOs: 188, 181, 182, and 215; e.) SEQ ID NOs: 228, 181, 182, and 215; f.) SEQ ID NOs: 188, 181, 278, and 183; and g.) SEQ ID NOs: 284, 181, 286, and 183. In some embodiments, each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 180-183, 188, 190, 212, 215, 228, 278, 284 or 286. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, including any of the foregoing, the sdAb, optionally a VHH domain, comprises: a FR1 comprising or consisting of the amino acid sequence X1VX2LX3ESGGGLVQPGGSLRLSX4AASG (SEQ ID NO: 300), wherein X1is E or G, X2is Q or R; X3 is L or V; and X4 is A or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1 is E; X2 is Q; X3 is L; and X4 is A or C; a FR2 comprising or consisting of the amino acid sequence SEQ ID NO: 301; a FR3 comprising or consisting of the amino acid sequence RFX1ISRDNSKNTLYLQMNX2LRAX3DTAVYYX4 (SEQ ID NO: 302), wherein X1 is T or S; X2 is S or G; X3 is E or A; X4 is A, V, or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1is R; X2is S; X3is E; and X4is A or C; and a FR4 comprising or consisting of the amino acid sequence WGX1GTQVTVSS (SEQ ID NO: 303), wherein X1 is Q or R; or optionally a conservative substitution of any of the foregoing; optionally wherein X1 is Q. In some embodiments, including any of the foregoing, the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288 or 296. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 177-179, 185-186, 194-195, 201, 202, 209-211, 217-219, 225-226, 233-234, 241-242, 249-251, 257, 265-267, 273-274, 281-283, or 289-290, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 180-183, 188, 190, 212, 215, 228, 278, 284 or 286. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, including any of the foregoing, the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288 or 296. A. Exemplary mcyV.0300 Variant Anti-Myc sdAb In some embodiments, including any of the exemplary anti-Myc sdAbs disclosed above and elsewhere herein, the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AALGDYGX1AIDYSEADY (SEQ ID NO: 306), wherein X1 is D or G; or optionally a conservative substitution of any of the foregoing. In some embodiments, the CDR3 comprises or consists of any one of SEQ ID NOs: 179 or 195. In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 177, 185, or 201; a CDR2 comprising or consisting of any one of SEQ ID NOs: 178, 186, 194 or 202; and a CDR3 comprising or consisting of any one of SEQ ID NOs: 179 or 195. In some embodiments, the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a.) SEQ ID NOs: 177, 178, and 179; b.) SEQ ID NOs: 185, 186, and 179; c.) SEQ ID NOs: 177, 194, and 195; and d.) SEQ ID NOs: 201, 202, and 179. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 177-179, 185-186, 194-195, or 201-202. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3X4MX5(SEQ ID NO: 304), wherein X1 is A, S or E; X2 is D, T, or G; X3 is T, M or Q; X4 is D or P; and X5 is G or S; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISX1X2X3X4X5TYYADSVX6G (SEQ ID NO: 305), wherein X1is G or A; X2is S or D; X3is G or A; X4is G, D, or E; X5is N, V or A; and X6 is K or R; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence AALGDYGX1AIDYSEADY (SEQ ID NO: 306), wherein X1is D or G; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.0300 (SEQ ID NOs: 139, 141 and 143). In some embodiments, the sdAb, optionally a VHH domain, comprises a VHFR1 comprising or consisting of any one of SEQ ID NOs: 180 or 188, a VH FR2 comprising or consisting of SEQ ID NO: 181, a VH FR3 comprising or consisting of any one of SEQ ID NOs: 182 or 190, and a VHFR4 comprising or consisting of SEQ ID NO: 183, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a.) SEQ ID NOs: 180, 181, 182, and 183; b.) SEQ ID NOs: 188, 181, 190, and 183; and c.) SEQ ID NOs: 188, 181, 182, and 183. In some embodiments, each VHframework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 180-183, 188 or 190. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 184, 192, 200, 208, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 177-179, 185-186, 194-195, or 201-202, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 180-183, 188 or 190. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 184, 192, 200, 208. B. Exemplary mcyV.1300 Variant Anti-Myc sdAb In some embodiments, including any of the exemplary anti-Myc sdAbs disclosed above and elsewhere herein, the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AX1LX2QELTGASEHDY (SEQ ID NO: 309), wherein X1is H or Y; and X2is D or G; or optionally a conservative substitution of any of the foregoing. In some embodiments, the CDR3 comprises or consists of SEQ ID NO: 211. In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of SEQ ID NO: 209, a CDR2 comprising or consisting of SEQ ID NO: 210, and a CDR3 comprising or consisting of SEQ ID NO: 211. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 209-211. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3X4MG (SEQ ID NO: 307), wherein X1is G or D; X2 is D or E; X3 is A or T; and X4 is D or A; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISASX1X2X3TYYADSVKG (SEQ ID NO: 308), wherein X1is G or S; X2is D or A; and X3is X or E; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence AX1LX2QELTGASEHDY (SEQ ID NO: 309), wherein X1is H or Y; and X2is D or G; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.1300 (SEQ ID NOs: 147, 149 and 151). In some embodiments, the sdAb, optionally a VHH domain, comprises a VHFR1 comprising or consisting of SEQ ID NO: 212, a VHFR2 comprising or consisting of SEQ ID NO: 213 a VHFR3 comprising or consisting of SEQ ID NO: 214, and a VH FR4 comprising or consisting of SEQ ID NO: 215. In some embodiments, each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 212-215. In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of a sequence that is SEQ ID NO: 216. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 209-211, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 212-215. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to SEQ ID NO: 216. In some embodiments, the substitution(s) are conservative substitution(s). C. Exemplary mcyV.1500 Variant Anti-Myc sdAb In some embodiments, including any of the exemplary anti-Myc sdAbs disclosed above and elsewhere herein, the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of the amino acid sequence AIIDDILTX1GTFDEGDY (SEQ ID NO: 312), wherein X1 is G or D; or optionally a conservative substitution of any of the foregoing. In some embodiments, the CDR3 comprises or consists of any one of SEQ ID NOs: 219 or 251. In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 217, 225, 233, 241, 249 or 257; a CDR2 comprising or consisting of any one of SEQ ID NOs: 218, 226, 234, 242 or 250, and a CDR3 comprising or consisting of any one of SEQ ID NOs: 219 or 251. In some embodiments, the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a.) SEQ ID NOs: 217, 218, and 219; b.) SEQ ID NOs: 225, 226, and 219; c.) SEQ ID NOs: 233, 234, and 219; d.) SEQ ID NOs: 241, 242, and 219; e.) SEQ ID NOs: 249, 250, and 251; and f.) SEQ ID NOs: 257, 218, and 219. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 217-219, 225-226, 233-234, 241-242, 249-251, and 257. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FX1FX2X3X4X5MG (SEQ ID NO: 310), wherein X1 is T or D; X2 is A, E, D, S or G; X3 is D, E or T; X4 is T, H, Y, V or A; and X5 is D, A or S; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISX1X2X3X4X5X6YYADSVKG (SEQ ID NO: 311), wherein X1is G, P, R or A; X2is S or D; X3 is G or A; X4 is G, A, T or D; X5 is S, T, A or V; and X6 is T or A; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence AIIDDILTX1GTFDEGDY (SEQ ID NO: 312), wherein X1is G or D; or optionally a conservative substitution of any of the foregoing; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.1500 SEQ ID NOs: (155, 157 and 159). In some embodiments, the sdAb, optionally a VHH domain, comprises a VH FR1 comprising or consisting of any one of SEQ ID NOs: 220 or 228, a VH FR2 comprising or consisting of SEQ ID NO: 221, a VH FR3 comprising or consisting of SEQ ID NO: 222, and a VHFR4 comprising or consisting of SEQ ID NO: 223, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a) SEQ ID NOs: 220, 221, 222, and 223; and b) SEQ ID NOs: 228, 221, 222, and 223. In some embodiments, each VHframework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 220-223, or 228. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 224, 232, 240, 248, 256 or 264, optionally wherein each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 217-219, 225-226, 233-234, 241- 242, 249-251, or 257; and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 220-223, or 228. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 224, 232, 240, 248, 256 or 264. D. Exemplary mcyV.3700 Variant Anti-Myc sdAb In some embodiments, including any of the exemplary anti-Myc sdAbs disclosed above and elsewhere herein, the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of SEQ ID NO: 267. In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 265 or 273, a CDR2 comprising or consisting of any one of SEQ ID NOs: 266 or 274, and a CDR3 comprising or consisting of SEQ ID NO: 267. In some embodiments, the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: a) SEQ ID NOs: 265, 266, and 267; and b) SEQ ID NOs: 273, 274, and 267. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 265-267, or 273-274. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3DMG (SEQ ID NO: 313), wherein X1 is D, G or E; X2 is V, S or G; and X3 is S, N, or Q; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AIX1X2X3X4X5X6TYYADSVKG (SEQ ID NO: 314), wherein X1is no amino acid or S; X2 is G or S; X3 is T, G, or S; X4 is E or G; X5 is G, D or E; and X6 is D, T or H; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence SEQ ID NO: 315; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.3700 SEQ ID NOs: (163, 165 and 167). In some embodiments, the sdAb, optionally a VHH domain, comprises a VHFR1 comprising or consisting of SEQ ID NO: 268, a VHFR2 comprising or consisting of SEQ ID NO: 269, a VHFR3 comprising or consisting of any one of SEQ ID NOs: 270 or 278, and a VH FR4 comprising or consisting of SEQ ID NO: 271, optionally wherein the combination of FR1, FR2, FR3, and FR4 is selected from one of the following combinations: a) SEQ ID NOs: 268, 269, 270, and 271; and b) SEQ ID NOs: 268, 269, 278, and 271. In some embodiments, each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 268-271, or 278. In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 272 or 280. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 265-267, or 273-274, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 268-271, or 278. In some embodiments, In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 272 or 280. In some embodiments, In some embodiments, the substitution(s) are conservative substitution(s). E. Exemplary mcyV.6600 Variant Anti-Myc sdAb In some embodiments, including any of the exemplary anti-Myc sdAbs disclosed above and elsewhere herein, the sdAb, optionally a VHH domain, comprises a CDR3 comprising or consisting of SEQ ID NO: 283. In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of any one of SEQ ID NOs: 281 or 289, a CDR2 comprising or consisting of any one of SEQ ID NOs: 282 or 290, and a CDR3 comprising or consisting of SEQ ID NO: 283. In some embodiments, the combination of CDR1, CDR2, and CDR3 is selected from one of the following combinations: SEQ ID NOs: 281, 282, and 283; and b) SEQ ID NOs: 289, 290, and 283. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 281-283, and 289-290. In some embodiments, In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises: a CDR1 comprising or consisting of the amino acid sequence FTFX1X2X3AMX4(SEQ ID NO: 316), wherein X1 is S or D, X2 is S, E or D; X3 is Y or H; and X4 is S or G; or optionally a conservative substitution of any of the foregoing; a CDR2 comprising or consisting of the amino acid sequence AISX1X2X3X4X5TYYADSVKG (SEQ ID NO: 317), wherein X1G or A; X2is S or D; X3is G or A; X4is G or S; and X5is S, V or T; or optionally a conservative substitution of any of the foregoing; and a CDR3 comprising or consisting of the amino acid sequence SEQ ID NO: 318; wherein the combination of CDR1, CDR2 and CDR3 is not the combination of CDR1, CDR2 and CDR3 of mycV.6600 SEQ ID NOs: (171, 173 and 175). In some embodiments, the sdAb, optionally a VHH domain, comprises a VH FR1 comprising or consisting of SEQ ID NO: 284, a VH FR2 comprising or consisting of SEQ ID NO: 285, a VH FR3 comprising or consisting of SEQ ID NO: 286, and a VHFR4 comprising or consisting of SEQ ID NO: 287. In some embodiments, the combination of FR1, FR2, FR3, and FR4 is 284, 285, 286, and 287. In some embodiments, each VH framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 284, 285, 286, and 287. In some embodiments, In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of a sequence selected from any one of SEQ ID NOs: 288 or 296. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 281-283, and 289-290, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 284, 285, 286, and 287. In some embodiments, In some embodiments, the substitution(s) are conservative substitution(s). In some embodiments, the sdAb, optionally a VHH domain, comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 288 or 296. In some embodiments, In some embodiments, the substitution(s) are conservative substitution(s). F. Further Embodiments of Exemplary Anti-Myc sdAb In some embodiments, including any of the exemplary anti-Myc sdAbs and variant anti-Myc sdAbs disclosed above and elsewhere herein, the sdAb, optionally a VHH domain, comprises: a FR1 comprising or consisting of the amino acid sequence X1VX2LX3ESGGGLVQPGGSLRLSX4AASG (SEQ ID NO: 300), wherein X1is E or G, X2is Q or R; X3 is L or V; and X4 is A or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1is E; X2is Q; X3is L; and X4is A or C; a FR2 comprising or consisting of the amino acid sequence SEQ ID NO: 301; a FR3 comprising or consisting of the amino acid sequence RFX1ISRDNSKNTLYLQMNX2LRAX3DTAVYYX4 (SEQ ID NO: 302), wherein X1 is T or S; X2 is S or G; X3 is E or A; X4 is A, V, or C; or optionally a conservative substitution of any of the foregoing; optionally wherein X1is R; X2is S; X3is E; and X4 is A or C; and a FR4 comprising or consisting of the amino acid sequence WGX1GTQVTVSS (SEQ ID NO: 303), wherein X1 is Q or R; or optionally a conservative substitution of any of the foregoing; optionally wherein X1is Q. In some embodiments, the sdAb comprises a VHH domain with a substitution at C22 of FR1 and / or C30 of FR3, optionally wherein the substitution is independently selected from a C to A and a C to V substitution. In some embodiments, the sdAb has a Kd value of less than 1x10-7and optionally at least 1x10-10, optionally wherein the Kd is 1.49x10-7to 5.56x10-9. In some embodiments, the Kd value is calculated using human c-Myc, optionally as described for values of Octet sdAb Kd Human Myc Peptide Monovalent (M) in Example 4. In some embodiments, the sdAb has a Poly Specificity Reagent (PSR) score of less than 1, optionally less than 0.43, optionally less than 0.26. In some embodiments, the sdAb has a PSR score of at least 0.01, optionally at least 0.26, optionally at least 0.43. In some embodiments, the sdAb has a PSR score of 1 to 0.01, 0.43 to 0.01, or 0.26 to 0.01. In some embodiments, the sdAb has a melting temperature (TM) of at least 40℃, optionally at least 45.5℃, optionally at least 64℃. In some embodiments, the sdAb has a TM of less than 70℃, optionally wherein the TM is 45℃ to 65℃. In some embodiments, any of the foregoing measures are calculated as detailed in Example 4. In some embodiments, the sdAb binds, or binds at least in part, to at least a portion of amino acids 410-419 of MYC (SEQ ID NO: 1). In some embodiments, the sdAb binds, or binds at least in part, to at least a portion of a peptide consisting of SEQ ID NO: 769. In some embodiments, the sdAb binds, or binds at least in part, to at least a portion of a peptide consisting of SEQ ID NO: 770. In some embodiments, the sdAb binds, or binds at least in part, to at least a portion of a peptide consisting of SEQ ID NO: 771. In some embodiments, the sdAb binds, or binds at least in part, to at least a portion of amino acids 410-419 of MYC (SEQ ID NO: 1), and / or one or more of SEQ ID NOs: 769-771. In some embodiments, the sdAb does not comprise or consist of any one of SEQ ID NO: 138-176 and 641-768. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, a polypeptide comprising or consisting of an anti-Myc sdAb disclosed above and elsewhere herein can be utilized as a myc-binding moiety in a larger polypeptide, compound or conjugate. In some embodiments, a polypeptide comprising or consisting of an anti-Myc sdAb disclosed herein is conjugated to a therapeutic compound such as a drug (e.g., a chemotherapeutic drug or agent). In some embodiments, a polypeptide comprising or consisting of an anti-Myc sdAb disclosed herein is conjugated to a detectable label (e.g., a radioisotope, fluorescent molecule, etc.). Also disclosed herein are polynucleotides encoding for any of the polypeptides comprising or consisting of the anti-Myc sdAb disclosed above and elsewhere herein. Portions / URDs of E3 Ubiquitin Ligases and Viral Homologs Disclosed herein are polypeptides comprising or consisting of a portion derived from a protein selected from the group consisting of a RING family E3 ubiquitin ligase, a cullin family E3 ubiquitin ligase, a homologous to E6AP carboxyl terminus (HECT) family E3 ubiquitin ligase, and a viral homolog of an E3 ubiquitin ligase. In some embodiments the viral homolog is VIF of HIV-1. In some embodiments, the portion comprises an amino acid substitution (optionally a conservative substitution), addition, and / or deletion to the protein. In some embodiments, the deletion is not an end terminal deletion or truncation of the protein. In some embodiments, the polypeptide and / or the portion is a non-natural polypeptide. In some embodiments, the portion has ubiquitin-proteasome recruiting activity. In some embodiments, the portion is a URD that has ubiquitin-proteasome recruiting activity. In some embodiments the portion of E3 ligase or viral homolog is fused to a polypeptide. In some embodiments, the fusion polypeptide comprises a linker, localization sequence (e.g., NLS), first and / or second targeting moiety, and / or other polypeptide disclosed herein. In some embodiments, the portion is derived from an E3 ubiquitin ligase selected from the group consisting of CHIP, DCAF1, E6AP, FBXW7-alpha (also referred to herein as “FBXW7a”), FBXW7-beta (also referred to herein as “FBXW7b”), Keap1, NHLRC1, RNF4, RNF6, RNF11, RNF12, RNF20, RNF25, RNF111, RNF114, RNF115, RNF125, RNF128, RNF138, RNF149, RNF152, RNF165, RNF166, RNF182, SPOP, beta-TRCP, TRIM21, TRIM32, VIF, ZNRF1, ZNRF4, and CBL-b (Y363E). Table 23 below discloses representative sequences of the preceding. In some embodiments, the portion is selected from the group consisting of CBLb.1, CHIP.1, DCAF1.1, E6AP.1, FBXW7a.1, FBXW7a.2, FBXW7a.3, FBXW7a.4, FBXW7a.5, FBXW7a.6, FBXW7a.7, FBXW7a.8, FBXW7a.9, FBXW7b.1, FBXW7b.2, FBXW7b.3, FBXW7b.4, Keap1.1, NHLRC1.1, NHLRC1.2, NHLRC1.3, NHLRC1.4, NHLRC1.5, RNF4.1, RNF6.1, RNF6.2, RNF11.1, RNF12.1, RNF12.2, RNF20.1, RNF25.1, RNF111.1, RNF114.1, RNF115.1, RNF125.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF125.7, RNF128.1, RNF138.1, RNF149.1, RNF152.1, RNF165.1, RNF166.1, RNF182.1, RNF182.2, SPOP.1, SPOP.2, SPOP.3, bTRCP.1, TRIM21.1, TRIM21.2, TRIM21.3, TRIM32.1, VIF.1, ZNRF1.1, and ZNRF4.1. Table 24 below discloses representative sequences of the preceding. In some embodiments, the portion is derived from a monomeric RING family E3 ligase. In some embodiments, the portion is derived from a monomeric RING family E3 ligase selected from the group consisting of NHLRC1, RNF11, RNF111, RNF114, RNF115, RNF12, RNF125, RNF128, RNF138, RNF149, RNF152, RNF165, RNF166, RNF182, RNF20, RNF25, RNF4, RNF6, ZNRF1, ZNRF4, and CBL-b (Y363E). In some embodiments, the portion is derived from a monomeric RING family E3 ligase selected from the group consisting of RNF125, NHL, RC1, RNF4, RNF6, RNF12, RNF138 and ZNRF1. In some embodiments, the portion is selected from the group consisting of NHLRC1.1, NHLRC1.2, NHLRC1.3, NHLRC1.4, NHLRC1.5, RNF11.1, RNF111.1, RNF114.1, RNF115.1, RNF12.1, RNF12.2, RNF125.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF125.7, RNF128.1, RNF138.1, RNF149.1, RNF152.1, RNF165.1, RNF166.1, RNF182.1, RNF182.2, RNF20.1, RNF25.1, RNF4.1, RNF6.1, RNF6.2, ZNRF1.1, ZNRF4.1, and CBLb.1. In some embodiments, the portion is selected from the group consisting of NHLRC1.1, NHLRC1.2, NHLRC1.3, NHLRC1.4, NHLRC1.5, RNF125.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF125.7, RNF4.1, RNF6.1, RNF6.2, RNF12.1, RNF12.2, RNF138.1, and ZNRF1.1. In some embodiments, the portion is derived from a cullin family E3 ligase. In some embodiments, the portion is derived from a cullin family E3 ligase selected from the group consisting of DCAF1, beta-TRCP, FBXW7-alpha, FBXW7-beta, Keap1, and SPOP. In some embodiments, the portion is derived from a cullin family E3 ligase selected from the group consisting of beta-TRCP, FBXW7-alpha, and FBXW7-beta. In some embodiments, the portion is selected from the group consisting of DCAF1.1, bTRCP.1, FBXW7a.1, FBXW7a.2, FBXW7a.3, FBXW7a.4, FBXW7a.5, FBXW7a.6, FBXW7a.7, FBXW7a.8, FBXW7a.9, FBXW7b.1, FBXW7b.2, FBXW7b.3, FBXW7b.4, Keap1.1, SPOP.1, SPOP.2, and SPOP.3. In some embodiments, the number of amino acids in the portion is, is about, or is less than, 80, 75, 70, 65, 60, 65, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or 1%, of the number of amino acids in the wild-type full-length protein (e.g. sequences disclosed in Table 23), or a range defined by any two of the preceding values, optionally 15-80, 15-50, 25-80, 25-50, 30- 60, 1-80, 2-80, 1-70, 2-70, 2-65%. In some embodiments, the number of amino acids in the portion is, or is about 15-50% of the number of amino acids in the wild-type full-length protein. In some embodiments, the number of amino acids in the portion is, or is about, 2-61% of the number of amino acids in the wild-type full-length protein. In some embodiments, the portion is, is about, is less than or equal to 370, 369, 368, 367, 366, 365, 364, 363, 362, 361, 360, 300, 250, 200, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 120, 115, 110, 105, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 25, or 20 amino acids long, or a range defined by any two of the preceding values. In some embodiments, the portion is, or is about, 20-370, 20-150, 20- 100, 20-80, 30-150, 30-100, 50-150 amino acids long. In some embodiments, the portion is, or is about, 50-100 or 20-100 amino acids long. In some embodiments, the portion is, or is about, 40-130 or 44-126 amino acids long. In some embodiments, the portion comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 39-113, optionally SEQ ID NOs: 54-113, optionally wherein the portion has ubiquitin-proteasome recruiting activity. In some embodiments, the portion comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 76-106 and 111-113, optionally wherein the portion has ubiquitin-proteasome recruiting activity. In some embodiments, the portion comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 76-80, 85-93, 95, 104-106, and 111, optionally wherein the portion has ubiquitin-proteasome recruiting activity. In some embodiments, the portion consists of an amino acid sequence selected from any one of SEQ ID NOs: 76-80, 85- 93, 95, 104-106, and 111. In some embodiments, the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 39-113. In some embodiments, , the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of any one of SEQ ID NO: 54-113. In some embodiments, the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 76, 88, 98, 104 and 111. In some embodiments, the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 76, 88, 98, and 104. In some embodiments, the URD comprises or consists of a truncation or fragment of one of the forgoing that retains ubiquitin- proteasome recruiting activity. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the portion comprises an amino acid substitution, addition, and / or deletion to the protein. In some embodiments, the deletion is not an end terminal deletion or truncation of the protein. In some embodiments, the polypeptide and / or the portion is a non-natural polypeptide. In some embodiments, the portion is a URD that has ubiquitin- proteasome recruiting activity. In some embodiments, disclosed herein are bifunctional polypeptides, optionally dual-specific, comprising the polypeptide comprising or consisting of the portion derived from a protein selected from the group consisting of a RING family E3 ubiquitin ligase, a cullin family E3 ubiquitin ligase, a homologous to E6AP carboxyl terminus (HECT) family E3 ubiquitin ligase, and a viral homolog of an E3 ubiquitin ligase, as described in the paragraphs above and elsewhere herein, wherein the bifunctional polypeptide comprises: a) the portion of the protein and, b) a first and optionally a second targeting moiety (also referred to as a target “binder” or “binding moiety”) that is capable of binding to a first (e.g., Myc) and optionally a second target protein, optionally the same target protein, optionally an intracellular target protein(s). In some embodiment the first and / or second targeting moiety binds selectively or specifically to the target protein(s). In some embodiments, the first targeting moiety, and optionally the second targeting moiety, comprises or consists of an anti-Myc sdAb disclosed herein. In some embodiments, the bifunctional polypeptides, optionally dual-specific, promote proteasome-mediated degradation of a target protein or proteins. In some embodiments, proximity of the bifunctional polypeptide to the target protein(s) through binding of the targeting moiety induces ubiquitination of the target protein(s) via the URD, thereby promoting proteasome-mediated degradation of the target protein(s). In some embodiments one or both of the target protein(s) is an intracellular target protein. In some embodiments, the bifunctional polypeptide that promotes proteasome-mediated degradation of a target protein(s), comprises or consisting of the polypeptide of comprising or consisting of the portion derived from a protein selected from the group consisting of a RING family E3 ubiquitin ligase, a cullin family E3 ubiquitin ligase, a homologous to E6AP carboxyl terminus (HECT) family E3 ubiquitin ligase, and a viral homolog of an E3 ubiquitin ligase, as described in the paragraphs above and elsewhere herein. In some embodiments of the bifunctional polypeptide that promotes proteasome-mediated degradation of a target protein(s), the URD consists of the URD derived from a protein selected from the group consisting of a RING family E3 ubiquitin ligase, a cullin family E3 ubiquitin ligase, a homologous to E6AP carboxyl terminus (HECT) family E3 ubiquitin ligase, and a viral homolog of an E3 ubiquitin ligase, as described in the paragraphs above and elsewhere herein. In some embodiment the first and / or second targeting moiety binds selectively or specifically to the target protein(s). Any combination of the targeting moieties and the URD disclosed herein may be used in the construction of the bifunctional polypeptide. Table 23: Representative E3 ligases and viral homologs for derivation of portions Table 24: Exemplary Portions / URDs derived from E3 ligases and viral homologs In some embodiments, the component of the dual-specific bifunctional polypeptide that is capable of recruiting the ubiquitination complex is generally composed of a URD. In some embodiments, the URD may be derived from an E3 ubiquitin ligase, such as a human E3 ubiquitin ligase. However, in some embodiments, the URD does not strictly need to be derived from an E3 ubiquitin ligase, and may otherwise be derived from other sources, such as viral analogues of E3 ubiquitin ligases that have ubiquitin complex recruitment function (for example, the VIF protein of HIV). The URD may be derived from any of the diverse family of E3 ubiquitin ligases based on factors such as size, localization in the cell (e.g., cytoplasm and / or nucleus), and orientation of the URD domain within the E3 ubiquitin ligase (i.e., if the URD appears N-terminally or C-terminally to the substrate recognition domain). In some embodiments, exemplary URD domains may include, but are not limited to, U-box, RING, HECT, F-box (Cul1-SKP1), BTB (Cul3), and H-box (Cul4-DDB1) domains. In some embodiments, exemplary URDs may be derived from E3 ubiquitin ligases including but not limited to CHIP (also termed STUB1), RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL- b (Y363E), TRIM21, E6AP, FBXW7 alpha, FBXW7 beta, beta-TRCP, Keap1, SPOP, or DCAF1. It is envisioned that any truncation or fragment of these E3 ubiquitin ligases that retain ubiquitin-proteasome recruiting activity may be used as a URD in the embodiments herein. In some embodiments, the URD is derived from a RING domain (e.g., RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E)) or an H-box (Cul4-DDB1) domain (e.g., DCAF1), or any truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. The URD should be understood as a protein, or fragment or truncation thereof, that can function to recruit a ubiquitination complex (e.g., can recruit an E2 ubiquitin conjugating enzyme). In some embodiments, the URD is derived from an E3 ubiquitin ligase. In some embodiments, the URD is derived from CHIP, RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E), TRIM21, E6AP, FBXW7 alpha, FBXW7 beta, beta-TRCP, Keap1, SPOP, or DCAF1, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD is derived from CHIP, RNF114, RNF125 (e.g., RNF125.2), RNF138, RNF166, NHLRC1, CBL-b (Y363E), TRIM21, E6AP, FBXW7 alpha, FBXW7 beta, beta-TRCP, Keap1, SPOP (e.g., SPOP.2 or SPOP.3), or DCAF1, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD is selected from a RING domain and an H-box (Cul4-DDB1) domain, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the RING domain is RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E), or TRIM21. In some embodiments, the H-box domain is DCAF1. In some embodiments, the URD is selected from: the URD derived from a protein which localizes to the cytoplasm; the URD derived from a protein which localizes to the nucleus; and the URD derived from a protein which localizes to the cytoplasm and the nucleus; or a truncation or fragment of the URD that retains ubiquitin-proteasome recruiting activity. In some embodiments, the protein which localizes to the cytoplasm is FBXW7 beta. In some embodiments, the protein which localizes to the nucleus is selected from FBXW7 alpha and SPOP. In some embodiments, the protein which localizes to the cytoplasm and the nucleic is selected from CHIP, RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E), TRIM21, E6AP, and DCAF1. In some embodiments, the URD is derived from an E3 ligase selected from the group consisting of NHLRC1, DCAF1, RNF125, RNF165, RNF4, and SPOP. In some embodiments, the URD is derived from an E3 ligase selected from the group consisting of optionally NHLRC1, RNF125, RNF165, RNF4 and SPOP. In some embodiments, the URD is derived from an E3 ligase selected from the group consisting of optionally NHLRC1, RNF125, RNF165, and RNF4. In some embodiments, the URD is selected from the group consisting of NHLRC1.1, DCAF1.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF165.1, RNF4.1, SPOP.2, and SPOP.3. In some embodiments, the URD is selected from the group consisting of NHLRC1.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, RNF165.1, RNF4.1, SPOP.2, and SPOP.3. In some embodiments, the URD is selected from the group consisting of NHLRC1.1, RNF125.2, RNF165.1, and RNF4.1. In some embodiments, the protein is an E3 ubiquitin ligase. In some embodiments, the URD is, is about, is at least, is at least about, is not more than, or is not more than about, 370, 369, 368, 367, 366, 365, 364, 363, 362, 361, 360, 300, 250, 200, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 120, 115, 110, 105, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 25, or 20 amino acids long, or a range defined by any two of the preceding values, for example, 370- 20, 370-120, 120-20, 80-20, or 360-150 amino acids long. In some embodiments, the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 39-53, or a truncation or fragment thereof that retains ubiquitin- proteasome recruiting activity. In some embodiments, the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 54- 113, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 73, 74, 76, 88-92, 98, and 104, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 76, 88, 98, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the URD is selected from: a URD derived from a protein which localizes to the cytoplasm, optionally selected from FBXW7 beta and Keap1; a URD derived from a protein which localizes to the nucleus, optionally selected from FBXW7 alpha, RNF165, and SPOP; and a URD derived from a protein which localizes to the cytoplasm and the nucleus, optionally selected from beta-TRCP, CHIP, RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E), TRIM21, E6AP, DCAF1 VIF, RNF11, RNF111, RNF115, RNF12, RNF128, RNF149, RNF152, RNF165, RNF182, RNF20, RNF25, RNF4, RNF6, TRIM32, ZNRF1, ZNRF4. Table 24 depicts various E3 ubiquitin ligases and respective URDs embodied herein. In some embodiments of the polypeptide comprising or consisting of a portion derived from a protein, the portion comprises an exemplary URD described below and / or in Table 24. In some embodiments of the dual-specific bifunctional polypeptide, the dual-specific bifunctional polypeptide comprises an exemplary URD described below and / or in Table 24. It is envisioned that alternative portions, fragments, or truncations of the E3 ubiquitin ligase proteins having ubiquitin-proteasome recruiting activity may also be used. Additional URDs are disclosed in PCT / US2023 / 066619, filed May 4, 2023, and PCT / US2023 / 76886, filed October 13, 2023, each of which is herein incorporated by reference in its entirety. Localization Sequences Localization of bifunctional polypeptides to the correct subcellular compartment may be important for the ability to degrade a target protein, e.g., if the target is localized to the nucleus, or if degradation of target protein only in the nucleus but not cytoplasm is desired. In some embodiments provided herein are polypeptides, or bifunctional polypeptides, optionally dual-specific, which are engineered (e.g., by modification of an endogenous localization peptide sequence, by adding localization peptide sequences, and / or by selecting a component which has an endogenous localization sequence) to direct the polypeptide or bifunctional polypeptide to a particular subcellular compartment, e.g., the cytoplasm, the nucleus, or both. In some embodiments, the polypeptide comprising a portion derived from an E3 ligase or viral homolog thereof comprises one or more localization peptide sequences. In some embodiments, the bifunctional polypeptide comprises one or more localization peptide sequences. In some embodiments, the polypeptide comprising a portion, or the bifunctional polypeptide comprises one or more localization peptide sequences that direct the polypeptide or bifunctional polypeptide to a subcellular compartment or compartments, optionally wherein the subcellular compartment is the nucleus and / or the cytoplasm. In some embodiments, the one or more localization peptide sequences direct the polypeptide or bifunctional polypeptide to a desired subcellular compartment or compartments, optionally wherein the one or more localization peptide sequences are selected or designed to direct the polypeptide or bifunctional polypeptide to a desired subcellular compartment or compartments. In some embodiments, the one or more localization peptide sequences comprise or consist of a nuclear localization signal (NLS) peptide and / or a nuclear export signal (NES) peptide. In some embodiments, the bifunctional polypeptide further comprises a nuclear localization signal (NLS) peptide. In some embodiments, the NLS peptide is located at the N-terminus of the bifunctional polypeptide, the C-terminus of the bifunctional polypeptide, or internally within the bifunctional polypeptide. In some embodiments, the NLS signal is an NLS that naturally occurs in one or more of the components of the bifunctional polypeptide, such as an NLS that is naturally found in the first and / or optional second targeting moiety and / or URD. For example, the first and / or optional second targeting moiety and / or URD of a bifunctional polypeptide may comprise an NLS within their sequence. In some embodiments the NLS is an NLS that is engineered into the bifunctional polypeptide, for example, added N-terminally, C-terminally, or internally within a component of the bifunctional polypeptide, such as the first and / or optional second targeting moiety and / or URD. In some embodiments, the NLS peptide comprises or consists of the amino acid sequence of SEQ ID NO: 51. However, other suitable NLS peptides generally known in the art may also be used. In some embodiments the localization sequence is a sequence from Table 25 or 26. In some embodiments, the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the first and / or optional second targeting moiety and / or URD. In some embodiments, the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the URD, for example the localization sequences disclosed in Table 26. In some embodiments, the URD is selected from: a URD derived from a protein which localizes to the cytoplasm, optionally selected from FBXW7 beta and Keap1; a URD derived from a protein which localizes to the nucleus, optionally selected from FBXW7 alpha, RNF165, and SPOP; and a URD derived from a protein which localizes to the cytoplasm and the nucleus, optionally selected from beta- TRCP, CHIP, RNF114, RNF125, RNF138, RNF166, NHLRC1, CBL-b (Y363E), TRIM21, E6AP, DCAF1 VIF, RNF11, RNF111, RNF115, RNF12, RNF128, RNF149, RNF152, RNF165, RNF182, RNF20, RNF25, RNF4, RNF6, TRIM32, ZNRF1, ZNRF4. In some embodiments, the one or more localization peptide sequences comprise or consist of an endogenous localization peptide sequence of the URD and / or first and / or optional second targeting moiety that is modified, wherein the modification alters the subcellular compartment or compartments to which the bifunctional polypeptide, optionally dual-specific, is directed as compared to the native endogenous localization peptide sequence. In some embodiments, the modification comprises or consists of a substitution, truncation or deletion of an endogenous localization peptide sequence. In some embodiments: b. the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the cytoplasm; c. the native endogenous localization peptide sequence directs the polypeptide to the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus; d. the native endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to only the cytoplasm; e. the native endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to only the nucleus; f. the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm; or g. the native endogenous localization peptide sequence directs the polypeptide to the cytoplasm, and the modified endogenous localization peptide sequence directs the polypeptide to the nucleus and the cytoplasm. In some embodiments, the one or more localization peptide sequences comprises or consists of an endogenous localization peptide sequence of the URD that is modified, wherein the native endogenous localization peptide sequence directs the polypeptide to the nucleus, and the modified endogenous localization peptide sequence directs the polypeptide to the cytoplasm. In some embodiments, the modified endogenous localization peptide sequence comprises or consists of a modified SPOP URD endogenous localization peptide sequence, optionally wherein the URD is SPOP.3. In some embodiments, the one or more localization peptide sequences comprise or consist of an exogenous localization peptide sequence. In some embodiments, the one or more localization peptide sequences comprise or consist of an NLS peptide that is or is a derivative of the NLS of MYC, simian virus 40 (SV40), SPOP, nucleoplasmin, 53BP1, Hrp1. In some embodiments, the one or more localization peptide sequences comprise or consists of an NLS sequence disclosed in Table 25. In some embodiments, the one or more localization peptide sequences comprise or consist of an NLS comprising or consisting of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 114-127, or SEQ ID NOs: 114-122. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the polypeptide comprising a portion derived from an E3 ligase or viral homolog thereof comprises 2, 3, 4, or more localization peptide sequences, optionally wherein the polypeptide comprises 2, 3, 4 or more copies of the same localization sequence in series. In some embodiments, the bifunctional polypeptide, optionally dual- specific, comprises 2, 3, 4, or more localization peptide sequences, optionally wherein the bifunctional polypeptide comprises 2, 3, 4 or more copies of the same localization sequence in series. In some embodiments, the polypeptide or the bifunctional polypeptide, optionally dual- specific, comprises one or more localization peptide sequences located at a location selected from the group consisting of: the N-terminus of the bifunctional polypeptide; the C-terminus of the bifunctional polypeptide; internally within the bifunctional polypeptide; as part of the URD, optionally an endogenous portion of the URD; as a part of the first and / or optional second targeting moiety, optionally an endogenous portion of the URD; and a combination of any of the foregoing. In some embodiments, a first localization peptide sequence is located at the N- terminus of the polypeptide or the bifunctional polypeptide and a second localization peptide sequence is located at the C-terminus of the polypeptide or the bifunctional polypeptide. Table 25: Exemplary NLS sequences Table 26: Exemplary URD endogenous NLS / NES sequences In some embodiments, the NLS peptide comprises or consists of the amino acid sequence of SEQ ID NOs: 51 or 1897-1903. In some embodiments, the NLS peptide is derived from MYC NLS, SV40 NLS, 3XMYC NLS, 3xSV40 NLS, SPOP NLS, nucleoplasmin NLS, 53BP1 NLS, or Hrp1 NLS (SEQ ID NOs: 51, 1897-1903. In some embodiments, other suitable NLS peptides generally known in the art are contemplated. Some URDSs derived from E3 ubiquitin ligases contain an endogenous NLS, for example, SPOP and SPOP.2. In some embodiments, the dual-specific bifunctional polypeptide contains a URD with an endogenous NLS. In some embodiments, the dual-specific bifunctional polypeptide contains a URD with an endogenous NLS and an exogenous NLS. In some embodiments, the dual-specific bifunctional polypeptide contains a URD with a truncated or deleted endogenous NLS (e.g., SPOP.3) and an exogenous NLS. Additional localization sequences are disclosed in PCT / US2023 / 066619, filed May 4, 2023, and PCT / US2023 / 76886, filed October 13, 2023, each of which is herein incorporated by reference in its entirety. Exemplary Bifunctional Degraders Targeting Myc The following characteristics may apply to embodiments of the bifunctional polypeptides disclosed herein. One exemplary target protein embodied herein is MYC proto- oncogene, bHLH transcription factor (Myc; c-Myc). In some embodiments, the Myc is a mutant form. An example sequence for MYC is provided as SEQ ID NO: 1 (Uniprot #P01106). Myc is a major oncogene involved in the pathology of many types of cancer, including solid tumors (including but not limited to hepatocellular carcinoma, liver metastases, and colorectal carcinoma) and hematological malignancies. In embodiments disclosed herein, the bifunctional polypeptide comprises a targeting moiety (also referred to as a “binder” or “binding moiety”) that is capable of binding to Myc. In some embodiments, the bifunctional polypeptide promotes proteasome-mediated degradation of at least one target protein. In some embodiments, the at least one target protein is Myc, optionally c-Myc. In some embodiments, the bifunctional polypeptide comprises: a first targeting moiety comprising or consisting of an anti-Myc sdAb disclosed above under the heading “Anti-Myc Single Domain Antibodies (sdAb)” and elsewhere herein and a URD. In some embodiments, proximity of the bifunctional polypeptide to at the least one target protein (e.g., Myc, c-Myc) through binding of the targeting moiety induces ubiquitination of the at least one target protein via the URD, thereby promoting proteasome-mediated degradation of the at least one target protein. In some embodiments, the bifunctional polypeptide further comprises a first linker peptide, optionally wherein the first linker peptide is positioned between the first targeting moiety and the URD. In some embodiments, the bifunctional polypeptide further comprises one or more localization peptide sequences. In some embodiment the first targeting moiety binds selectively or specifically to the target protein Myc, preferably c-Myc. In some embodiments, the first targeting moiety comprises or consists of a VHH, VH, or VNAR domain of a heavy chain antibody (HcAb). In some embodiments, the first targeting moiety comprises or consists of an anti-Myc sdAb, comprising or consisting of a VHdomain of an IgG antibody, or a VHH, or VHdomain of a heavy chain antibody (HcAb). In some embodiments, the first targeting moiety comprises or consists of a VHH domain. In some embodiments, the first targeting moiety comprises or consists of a sdAb and the first targeting moiety is, or is less than, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 122, 121, 120, 119, 118, 117, 116, 115, 114, 113, 112, 110, 109, 108, 107, 106, 105, 104, 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, or 90, amino acids long, or a range defined by any two of the preceding values, optionally 90-150, 90-130, 110-150, 110-130, 110-125, or 114-124 amino acids long. In some embodiments, the first targeting moiety that is capable of binding to Myc may be capable of binding, or binding at least in part, to at least a portion of Myc, such as the DNA binding domain of Myc. In some embodiments, the first targeting moiety that is capable of binding to Myc is capable of binding, or binding at least in part, to at least a portion of amino acids 54-406, amino acids 354-406 (the DNA binding domain of MYC that binds to Omomyc; as seen in PDB: 1NKP), or amino acids 408-437, of MYC (as represented as SEQ ID NO: 1). In some embodiments, the first targeting moiety that is capable of binding to Myc is capable of binding, or binding at least in part, to at least a portion of amino acids 410-419 of MYC (as represented as SEQ ID NO: 1), the binding epitope of antibody 9E10 (as seen in PDB: 2OR9). The bifunctional polypeptides disclosed herein that are specific for Myc may be used for the treatment of a cancer, for example, a cancer exhibiting elevated levels of Myc, for example solid tumors (including but not limited to hepatocellular carcinoma, liver metastases, and colorectal carcinoma) and hematological malignancies. In some embodiments, bifunctional polypeptide comprises a localization peptide sequence which directs the bifunctional polypeptide to the nucleus of a cell. In some embodiments, the localization peptide sequence comprises or consists of the NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin. In some embodiments, the localization peptide sequence comprises or consists of the NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1. In some embodiments, the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of SPOP, optionally SPNLS.2, MYC, optionally mycNLS, and Hrp1, optionally hrpNLS. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114, 122 and 116. In some embodiments of the bifunctional polypeptide, the URD is the URD of NHLRC1, RNF125, RNF165, RNF4, or ZNRF1, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD comprises or consists of NHLRC1.1, RNF125.2, RNF165.1, RNF4.1, or ZNRF1.1. In some embodiments, the URD comprises or consists of NHLRC1.1 RNF125.2, RNF165.1, or RNF4.1. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76-80, 87-93, 98, 104 and 111. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76, 88, 98, 104, and 111, In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76, 88, 98, and 104. FIG. 8 discloses embodiments of bifunctional polypeptides, with SEQ ID NOs 562- 577 being dual-specific bifunctional polypeptides. The description identifies the elements of the polypeptide in the N- to C-terminal direction. In some embodiments, the bifunctional polypeptide targeting Myc is one of the embodiments described in FIG. 8. In some embodiments, the bifunctional polypeptide comprises the embodiments in FIG. 8 sharing one or more elements or features. In some embodiments the shared element or feature is the target. In some embodiments the shared element or feature is the URD name (e.g., those in Table 24). In some embodiments the shared element or feature is protein from which the URD is derived (e.g., those listed in Table 23). In some embodiments the shared element or feature is one or more of the following: the target; the protein from which the URD is derived; the URD name; the type of targeting moiety (e.g., sdAb); the targeting moiety name (e.g., those in Table 28; note that “full” is not included in the names in FIG. 8); the NLS name (e.g. those in Tables 25 and 26); the linker name (e.g., those in Table 32); the position of the URD relative to the targeting moiety (upstream or downstream); and both the URD name and targeting moiety name. In some embodiments, the HA tag sequence (SEQ ID NO: 384) is excluded. In some embodiments of the bifunctional polypeptide the first targeting moiety comprises or consists of an anti-Myc sdAb disclosed above under the heading “Anti-Myc Single Domain Antibodies (sdAb)” and elsewhere herein. In some embodiments, the first targeting moiety comprises or consists of a VHH domain. In some embodiments, the bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 428-561, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). Table 27 provided below lists the results of HiBiT™ degradation studies utilizing exemplary embodiments of bifunctional polypeptides disclosed herein. The tables list a “Grade” of A, B, C or D for the level of degradation of each of the targeted proteins. Details regarding the experimental protocol are provided in the Examples section below. In some embodiments, the bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 27, optionally excluding any one of the SEQ ID NOs listed as having a MYC degradation Grade of D, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 27 listed as having a MYC degradation Grade of A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 27 listed as having a MYC degradation Grade of A or B, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 27 listed as having a MYC degradation Grade of C and / or D, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments of the bifunctional polypeptide the URD is not derived from CHIP, optionally wherein the URD does not comprise or consist of CHIP.1, optionally wherein the URD does not comprise or consist of SEQ ID NO: 54. Also disclosed herein is a polynucleotide encoding any of the bifunctional polypeptides targeting Myc disclosed above, and elsewhere herein. Table 27: Exemplary bifunctional polypeptides with sdAb targeting Myc Dual-Specific Bifunctional Polypeptides: General Characteristics The following characteristics may apply to embodiments of the dual-specific bifunctional polypeptides disclosed herein. In some embodiments, the dual-specific bifunctional polypeptide comprises the any one of the bifunctional polypeptides targeting Myc disclosed above and elsewhere herein, where the dual-specific bifunctional polypeptide further comprises a second targeting moiety that is capable of binding to at least one second target protein, optionally an intracellular target protein. In some embodiments of the dual-specific bifunctional polypeptide, proximity of the dual-specific bifunctional polypeptide to at least one target protein through binding of the first targeting moiety and / or the second targeting moiety induces ubiquitination of the at least one target protein via the URD, thereby promoting proteasome-mediated degradation of the at least one target protein. In some embodiments, the first and the second target proteins can be or are bound by the dual-specific bifunctional polypeptide simultaneously, in some embodiments only one of the first and second target proteins can be or are bound by the dual-specific bifunctional polypeptide at a time. In some embodiments, dual-specific bifunctional polypeptide further comprises a second linker peptide, wherein the second linker peptide is positioned between the second targeting moiety and the URD or between the first targeting moiety and the second targeting moiety. In some embodiments, the first targeting moiety binds to and / or is designed to bind a first target protein and the second targeting moiety binds to and / or is designed to bind a second target protein. In some embodiments, the first targeting moiety and the second targeting moiety bind to and / or are designed to bind to the same target protein, Myc. In some embodiments, the first targeting moiety binds to and / or is capable of binding to a first binding site of the target protein and the second targeting moiety binds to and / or is capable of binding to a second binding site of the target protein Myc. In some embodiments, the first targeting moiety and second targeting moiety bind to and / or are capable of binding to the same binding site of the target protein, wherein the dual-specific bifunctional polypeptide engages and / or is capable of engaging at least two molecules of the at least one target protein Myc. In some embodiments, the first and second targeting moieties are two copies of the same class of targeting, an anti- Myc sdAb, or two copies of the same anti-Myc sdAb. In some embodiments, the first and second targeting moieties target the same protein (Myc), but are not the same class of targeting moieties (e.g., an anti-Myc sdAb and an endogenous binding partner of the target protein such as omomyc). In some embodiments, the first targeting moiety targets Myc and the second targeting moiety targets different target protein. In some embodiment the first and / or second targeting moiety binds selectively or specifically to the target protein(s). In some embodiments, the second targeting moiety is, or is less than, 260, 259, 258, 257, 256, 255, 254, 253, 252, 251, 250, 245, 240, 235, 230, 225, 220, 215, 210, 205, 200, 195, 190, 185, 180, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 122, 121, 120, 119, 118, 117, 116, 115, 114, 113, 112, 110, 109, 108, 107, 106, 105, 104, 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 75, 70, 65, 60, 55, 54, 53, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10 amino acids long, or a range defined by any two of the preceding values, optionally 10-260, 10-200, 10-130, 25-260, 25-200, 25-130, 35-260, 35-200, 35-130, 50-260, 50-200, or 50-130 amino acids long. In some embodiments, the second targeting moiety comprises or consists of an endogenous binding partner of the target protein, an antibody, Fab, F(ab’)2, Fab’, scFv, single domain antibody (sdAb), VHdomain, VLdomain, VHH, VNAR, diabody, intrabody, DARPin, monobody, affibody, avimer, or any binding fragment or derivative thereof. In some embodiments, the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. In some embodiments, the second targeting moiety is, or is less than, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 75, 70, 65, 60, 55, 54, 53, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10 amino acids long, or a range defined by any two of the preceding values. In some embodiments, the second targeting moiety is 10-100, 10-25, 14-100, 14-25, 30-100, 30-50, 30-45, or 80-100 amino acids long. In some embodiments, the second targeting moiety comprises or consists of a sdAb. In some embodiments, the second targeting moiety comprises or consists of either a VHdomain or a VLdomain of an IgG antibody. In some embodiments, the second targeting moiety comprises or consists of a VHH, VH, or VNAR domain of a heavy chain antibody (HcAb). In some embodiments, the second targeting moiety comprises or consists of a VHH or VL domain. In some embodiments, the second targeting moiety comprises or consists of a sdAb and the second targeting moiety is, or is less than, 170, 165, 160, 155, 150, 145, 140, 135, 130, 129, 128, 127, 126, 125, 124, 123, 122, 121, 120, 119, 118, 117, 116, 115, 114, 113, 112, 110, 109, 108, 107, 106, 105, 104, 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, or 90, amino acids long, or a range defined by any two of the preceding values, optionally 90-150, 90-130, 110-150, 110-130, 110-125, or 114-124 amino acids long. In some embodiments, the second targeting moiety comprises or consists of an scFv. In some embodiments, the second targeting moiety comprises or consists of an scFv second targeting moiety is, or is less than, 260, 259, 258, 257, 256, 255, 254, 253, 252, 251, 250, 245, 240, 235, 230, 225, 220, 215, 210, 205, 200, 195, or 190 amino acids long, or a range defined by any two of the preceding values, optionally 190-260, 200-260, or 230-260 amino acids long. Exemplary Second Targets of Dual-Specific Bifunctional Polypeptides In some embodiments, the second target protein of the dual-specific bifunctional polypeptide (the first target protein being Myc) is generally a protein that is involved in disease pathology, for example, cancer. In some embodiments, the dual-specific bifunctional polypeptide comprises a second targeting moiety that is capable of binding (optionally selectively or specifically) to target protein selected from Myc, (optionally c-Myc), beta catenin 1 (CTNNB1), and proliferating cell nuclear antigen (PCNA). In some embodiments, the target protein is a wild-type and / or a mutant form of the target protein, optionally wherein the targeting moiety preferentially or selectively binds the mutant form of the target protein relative to the wild-type form of the target protein. In some embodiments, the mutant form of the target protein is CTNNB1 (SEQ ID NO: 2) comprising one or more mutations selected from: D32Y; D32N; D32V; D32G; S33Y; S33L; S33F; S33C; S33P; G34V; G34E; I35S; H36P; S37C; S37P; S37P and D207G; T41A; T41I; T42_K49del; S45F and Y670X wherein X indicates termination; S45C; S45F; S45P; S45Y; and S45del. In some embodiments of the dual-specific bifunctional polypeptide, the second targeting moiety binds, or binds at least in part, to at least a portion of: a) the DNA binding domain of MYC; b) the armadillo domain of CTNNB1, or c) the p21 binding domain of PCNA. In some embodiments, the second targeting moiety binds, or binds at least in part, to at least a portion of the target protein selected from the portion consisting of: a) amino acids 54-406 of MYC (SEQ ID NO: 1), b) amino acids 354-406 of MYC (SEQ ID NO: 1), c) amino acids 408-437 of MYC (SEQ ID NO: 1), d) amino acids 410-419 of MYC (SEQ ID NO: 1), e) amino acids 150-663 of CTNNB1 (SEQ ID NO: 2), f) amino acids 15-29 of CTNNB1 (SEQ ID NO: 2), g) amino acids 249-265, 292-306, 379-390, 415-429, 462-470, or 505-519, or any combination thereof, of CTNNB1 (SEQ ID NO: 2), and h) amino acids 38-48, 123-129, or 251-257 or any combination thereof, of PCNA (SEQ ID NO: 3). In some embodiments of the dual-specific bifunctional polypeptide, the second targeting moiety is selected from Omomyc, TCF4, TCF4.1, TCF4.2, TCF4.3, TCF4.4, TCF4.5, TCF4.6, TCF4.7, TCF4.8, TCF4.9, TCF4.10, TCF4.11, TCF4.12, TCF4.13, TCF4.14, TCF4.15, TCF4.16, con1.1, con1.2, p21.1, p21.2, p21.3, p21.4, p21.5, p21.6, p21.7, p21.8, p21.9, mycV.0300, mycV.1300, mycV.1500, mycV.3700, mycV.6600, mycV.1516, mycV.1515, mycV.1514, mycV.1513, mycV.1512, mycV.1511, mycV.1510, mycV.1509, mycV.1508, mycV.1507, mycV.1506, mycV.1505, mycV.1504, mycV.1503, mycV.1502, mycV.1501, , mycV.0302, mycV.0305, mycV.0306, mycV.0307, mycV.1308, mycV.1517, mycV.1518, mycV.1519, mycV.1520, mycV.1522, mycV.1524, mycV.3706, mycV.3708, mycV.6605, mycV.6608, or a fragment thereof that is capable of binding to the target protein. In some embodiments, the second targeting moiety does not comprise full length or unmodified con1 or p21. Exemplary sequences of second targeting moieties are found in Table 28. In some embodiments, the second targeting moiety comprises or consists comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 136, 137, 145, 153, 161, 169, 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, 319-344, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761. In some embodiments, the second targeting moiety comprises or consists comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, and 319-344. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. FIG. 8 discloses embodiments of dual-specific bifunctional polypeptides at SEQ ID NOs 562-577. The description identifies the elements of the polypeptide in the N- to C- terminal direction. In some embodiments, the dual-specific bifunctional polypeptide is or comprises one of the embodiments described in FIG. 8 at SEQ ID NOs: 562-577. In some embodiments, the dual-specific bifunctional polypeptide comprises one of the embodiments at SEQ ID NOs: 385-561 and further comprising a second targeting moiety. In some embodiments, the dual-specific bifunctional polypeptide comprises the embodiments in FIG.8 sharing one or more elements or features. In some embodiments the shared element or feature is the target(s). In some embodiments the shared element or feature is the URD name (e.g., those in Table 24). In some embodiments the shared element or feature is protein from which the URD is derived (e.g., those listed in Table 23). In some embodiments the shared element or feature is one or more of the following: the target; the protein from which the URD is derived; the URD name; the type of targeting moiety (e.g., sdAb, scFv, polypeptide binder); the targeting moiety name (e.g., those in Table 28; note that “full” is not included in the names in FIG.8); the NLS name (e.g. those in Tables 25 and 26); the linker name (e.g., those in Table 32); the position of the URD relative to the targeting moiety (upstream or downstream); and both the URD name and targeting moiety name. In some embodiments, the HA tag sequence (SEQ ID NO: 384) is excluded. In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 562-577. In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of SEQ ID NOs: 562-577. In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 562-577, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. Table 29 below lists the results of HiBiT™ degradation studies utilizing exemplary embodiments of dual-specific bifunctional polypeptides disclosed herein. The tables list a “Grade” of A, B, C or D for the level of degradation of each of the targeted proteins. For dual- specific bifunctional polypeptides where the first and the second targeting moieties target the same protein, only a single grade is provided, a grade for the second target is listed as “n.a.” signifying that it is not applicable. Details regarding the experimental protocol are provided in the Examples section below. In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 29 disclosing Grade A degradation of at least one of the target proteins, Grade B degradation of at least one of the target proteins, Grade C degradation of at least one of the target proteins, and / or Grade D degradation of at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 29 disclosing Grade A degradation of at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 disclosing Grade A degradation of at least one of the target proteins, and / or Grade B degradation of at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 disclosing a Combined Grade A / A or A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 disclosing a Combined Grade A / B or B / A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 disclosing a Combined Grade B / B or B, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 29 disclosing Grade A degradation of both target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 29 disclosing Grade C and / or D degradation of at least one of the target proteins, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide further shares one or more elements of features as described above and elsewhere herein. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. Table 28: Exemplary targeting moieties Table 29: Exemplary dual-specific bifunctional polypeptides targeting MYC and CTNNB1 and corresponding exemplary target protein degradation grade Exemplary Dual-Specific Bifunctional Degraders Targeting Myc In some embodiments, the at least one second target protein is Myc (c-Myc). In some embodiments, the Myc is a mutant form. An example sequence for Myc is provided as SEQ ID NO: 1 (Uniprot #P01106). In some embodiments, the dual-specific bifunctional polypeptide comprises a second targeting moiety that is capable of binding to Myc. Some examples of second targeting moieties that target Myc include Omomyc (SEQ ID NO: 4), although other suitable targeting moieties that bind to Myc generally known in the art may also be used. In some embodiments, the second targeting moiety that is capable of binding to Myc may be capable of binding, or binding at least in part, to at least a portion of Myc, such as the DNA binding domain of Myc. In some embodiments, the second targeting moiety that is capable of binding to Myc is capable of binding, or binding at least in part, to at least a portion of amino acids 54-406, amino acids 354-406 (the DNA binding domain of MYC that binds to Omomyc; as seen in PDB: 1NKP), amino acids 408-437, or amino acids 410-419 (binding epitope of antibody 9E10; as seen in PDB: 2OR9) of MYC (as represented as SEQ ID NO: 1). The dual- specific bifunctional polypeptides disclosed herein that are specific for Myc may be used for the treatment of a cancer, for example, a cancer exhibiting elevated levels of Myc, for example solid tumors (including but not limited to hepatocellular carcinoma, liver metastases, and colorectal carcinoma) and hematological malignancies. In some embodiments, the bifunction polypeptide targeting Myc comprises a localization peptide sequence which directs the dual-specific bifunctional polypeptide to the nucleus of a cell. In some embodiments, the localization peptide sequence comprises or consists of the NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin. In some, the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of SPOP, optionally SPNLS.2, MYC, optionally mycNLS, and Hrp1, optionally hrpNLS. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 122, 114 and 116. In some embodiments, the dual-specific bifunctional polypeptide targeting Myc comprises a URD derived from a URD selected from the group consisting of NHLRC1, RNF125, RNF165, and RNF4. In some embodiments, the URD is a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD comprises of consists of NHLRC1.1, RNF125.2, RNF165.1, or RNF4.1. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76-80, 87-93, 98, and 104. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NO: 76, 88, 98, and 104. In some embodiments, the dual-specific bifunctional polypeptide targeting Myc comprises a second targeting moiety that comprises or consists of a targeting moiety disclosed in Table 28 as targeting Myc. In some embodiments, the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. In some embodiments, the second targeting moiety comprises or consists of Omomyc, or a fragment thereof that is capable of binding to the target protein. In some embodiments, the second targeting moiety comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to SEQ ID NO: 136. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the dual-specific bifunctional polypeptide targeting Myc comprises a second targeting moiety that comprises or consists of a targeting moiety disclosed in Table 28 as targeting Myc. In some embodiments, the second targeting moiety comprises or consists of a sdAb, optionally comprising or consisting of either a VHdomain or a VLdomain of an IgG antibody, or a VHH, VH, or VNAR domain of a heavy chain antibody (HcAb). In some embodiments, the sdAb comprises or consists of a VHH domain. In some embodiments, the second targeting moiety comprises or consists of a sdAb, optionally a VHH domain, comprising a CDR1 selected from any one of SEQ ID NOs: 139, 147, 163, and 171, a CDR2 selected from any one of SEQ ID NOs: 141, 149, 157, and 165, and a CDR3 selected from any one of SEQ ID NOs: 143, 151, 159, 167, and 175. In some embodiments, the combination of CDR1, CDR2, and CDR3 is 1936, 157 and 159. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions (optionally conservative substitutions) and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 139, 147, 163, 171, 141, 149, 157, 165, 143, 151, 159, 167, and 175. In some embodiments, the sdAb, optionally a VHH domain, comprises a VH FR1 selected from any one of SEQ ID NOs: 138 and 170, a VHFR2 of SEQ ID NO: 140, a VHFR3 selected from any one of SEQ ID NOs: 142, 158, and 174, and a VH FR4 selected from any one of SEQ ID NOs: 144 and 152. In some embodiments, the combination of FR1, FR2, FR3 and FR4 is 154, 156, 158, and 160. In some embodiments, each VHframework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions (optionally conservative substitutions) and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 138, 170, 140, 142, 158, 174, 144, and 152. In some embodiments, the second targeting moiety comprises or consists of a sdAb, optionally a VHH domain, sequence selected from any one of SEQ ID NOs: 137, 145, 153, 161, 169, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761. In some embodiments, each CDR sequence independently comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions (optionally conservative substitutions) and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a CDR sequence of any one of SEQ ID NOs: 137, 145, 153, 161, 169, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761, and / or wherein the framework region comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more substitutions (optionally conservative substitutions) and / or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the framework region of any one of SEQ ID NOs: 137, 145, 153, 161, 169, 641, 649, 657, 665, 673, 681, 689, 697, 705, 713, 721, 729, 737, 745, 753, and 761. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the dual-specific bifunctional polypeptide targeting Myc comprises a second targeting moiety comprising or consisting of a sdAb, wherein the sdAb comprises or consists of a VHH domain. In some embodiments, the second targeting moiety comprises or consists of an anti-Myc sdAb described above under the heading “Anti-Myc Single Domain Antibodies (sdAb)”, and elsewhere herein. In some embodiments, the dual- specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 562, 565, 567, and 570-577, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting Myc comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 30, optionally excluding any one of the SEQ ID NOs having a Grade of D degradation of Myc and / or another target protein, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 30 having a Combined Grade A degradation of MYC, and / or a Combined Grade B degradation of MYC, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 30 having a Combined Grade of A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 30 having a Combined Grade of B, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 30 having a combined of Grade C and / or D, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting Myc comprises embodiments further sharing one or more elements or features. In some embodiments the shared element or feature is the URD name. In some embodiments the shared element or feature is protein from which the URD is derived. In some embodiments the shared element or feature is one or more of the following: the protein from which the URD is derived; the URD name; the type of targeting moiety; the targeting moiety name; the NLS name; the linker name; the position of the URD relative to the targeting moiety (upstream or downstream); and both the URD name and targeting moiety name. In some embodiments, the HA tag sequence (SEQ ID NO: 384) is excluded. In some embodiments of the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting Myc the URD is not derived from CHIP. In some embodiments, the URD does not comprise or consist of CHIP.1. In some embodiments, the URD does not comprise or consist of SEQ ID NO: 54. In some embodiments, disclosed herein is a polynucleotide encoding any of the dual- specific bifunctional polypeptides having a first and second targeting moiety targeting Myc disclosed above, or elsewhere herein. Table 30: Exemplary dual-specific bifunctional polypeptides comprising a first and second targeting moiety targeting MYC and corresponding exemplary target protein degradation grade Exemplary Dual-Specific Bifunctional Degraders Targeting Myc and CTNNB1 In some embodiments, the at least one second target protein is beta catenin 1 (CTNNB1). In some embodiments, the CTNNB1 is a mutant form. An example sequence for CTNNB1 is provided as SEQ ID NO: 2 (Uniprot #P35222). CTNNB1 is involved in the pathology of various solid tumors (including but not limited to liver metastases, colorectal carcinoma, or other gastrointestinal cancers) and hematological malignancies. In some embodiments disclosed herein, the dual-specific bifunctional polypeptide comprises a second targeting moiety that is capable of binding to CTNNB1. Some examples of targeting moieties that target CTNNB1 include TCF4 (SEQ ID NO: 6; Uniprot #Q9NQB0), and amino acids 10- 54 of TCF4 (SEQ ID NO: 5), although other suitable CTNNB1 targeting moieties generally known in the art may also be used. In some embodiments, the second targeting moiety that is capable of binding to CTNNB1 may be capable of binding, or binding at least in part, to at least a portion of CTNNB1, such as the armadillo domain of CTNNB1. In some embodiments, the second targeting moiety that is capable of binding to CTNNB1 is capable of binding, or binding at least in part, to at least a portion of amino acids 150-663 (the armadillo domain of CTNNB1; as seen in PDB: 2GL7), amino acids 15-29 (binding epitope of antibody BC2), or amino acids 249-265, 292-306, 379-390, 415-429, 462-470, or 505-519, (which are residues in the armadillo domain that interact with TCF4, E-cadherin, Axin, APC, TCF / LEF family transcription factors and / or SOX9) or any combination thereof, of CTNNB1 (as represented as SEQ ID NO: 2). The dual-specific bifunctional polypeptides disclosed herein comprising a second targeting moiety targeting CTNNB1 may be used for the treatment of a cancer, for example, a cancer involving nuclear expression of beta-catenin and / or harboring mutations or alterations in the Wnt / beta-catenin signaling pathway, for example, solid tumors (including but not limited to liver metastases, colorectal carcinoma, or other gastrointestinal cancers) and hematological malignancies. In some embodiments, the CTNNB1 target protein is a mutant form of CTNNB1 (SEQ ID NO: 2) comprising one or more mutations selected from: D32Y; D32N; D32V; D32G; S33Y; S33L; S33F; S33C; S33P; G34V; G34E; I35S; H36P; S37C; S37P; S37P and D207G; T41A; T41I; T42_K49del; S45F and Y670X wherein X indicates termination; S45C; S45F; S45P; S45Y; and S45del. In some embodiments, the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting CTNNB1 comprises a localization peptide sequence which directs the dual-specific bifunctional polypeptide to the nucleus of a cell. In some embodiments, the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin. In some embodiments, the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of MYC, optionally mycNLS, SPOP, optionally spNLS.2, and Hrp1, optionally hrpNLS. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 122, 114 and 116. In some embodiments, the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting CTNNB1 comprises a URD derived from a URD selected from the group consisting of NHLRC1, RNF125, RNF165, and RNF4, or a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD comprises or consists of NHLRC1.1, RNF125.2, RNF165.1, or RNF4.1. In some embodiments, the URD is a truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 6-80, 87-93, 98, and 104. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76, 88, 98, and 104. In some embodiments, the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting CTNNB1 comprises a second targeting moiety wherein the second targeting moiety comprises or consists of a targeting moiety disclosed in Table 28 as targeting CTNNB1. In some embodiments, the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. In some embodiments, In some embodiments, the second targeting moiety comprises or consists of TCF4.1, TCF4.2, TCF4.3, TCF4.4, TCF4.5, TCF4.6, TCF4.7, TCF4.8, TCF4.9, TCF4.10, TCF4.11, TCF4.12, TCF4.13, TCF4.14, TCF4.15, or TCF4.16, or a fragment thereof that is capable of binding to the target protein. In some embodiments, the second targeting moiety comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 319-333, optionally SEQ ID NO: 330. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the dual-specific bifunctional polypeptide targeting CTNNB1 comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 563, 564, 566, 568, and 569, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of the SEQ ID NOs in Table 31, optionally excluding any one of the SEQ ID NOs having a Grade of D degradation of CTNNB1 and / or MYC, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual- specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 31 having a Grade A degradation of CTNNB1, and / or a Grade B degradation of CTNNB1, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 31 having a Combined Grade of A and / or A / A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide comprises or consists of an amino acid sequence of any one of the SEQ ID NOs in Table 31 having a Combined Grade of A / B and / or B / A, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments, the dual-specific bifunctional polypeptide does not comprise or consist of an amino acid sequence of any one of the SEQ ID NOs in Table 31 having Grades C and / or D for either target protein, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384). In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the dual-specific bifunctional polypeptide targeting CTNNB1 comprises embodiments further sharing one or more elements or features. In some embodiments the shared element or feature is the URD name. In some embodiments the shared element or feature is protein from which the URD is derived. In some embodiments the shared element or feature is one or more of the following: the protein from which the URD is derived; the URD name; the type of targeting moiety; the targeting moiety name; the NLS name; the linker name; the position of the URD relative to the targeting moiety (upstream or downstream); and both the URD name and targeting moiety name. In some embodiments, the HA tag sequence (SEQ ID NO: 384) is excluded. In some embodiments of the dual-specific bifunctional polypeptide targeting CTNNB1 the URD is not derived from beta-TRCP. In some embodiments, the URD does not comprise or consist of bTRCP.1. In some embodiments, the URD does not comprise or consist of SEQ ID NOs: 57. In some embodiments, disclosed herein is a polynucleotide encoding any of the dual- specific bifunctional polypeptides targeting MYC and CTNNB1 disclosed above, or elsewhere herein. Table 31: Exemplary dual-specific bifunctional polypeptides targeting MYC and CTNNB1 and corresponding exemplary target protein degradation grade Exemplary Dual-Specific Bifunctional Degraders Targeting Myc and PCNA In some embodiments, the at least one second target protein is proliferating cell nuclear antigen (PCNA). In some embodiments, the PCNA is a mutant form. An example sequence for PCNA is provided as SEQ ID NO: 3 (Uniprot # P12004). PCNA is a co-factor for DNA polymerase delta and is involved in DNA synthesis and DNA repair. PCNA is implicated in the pathology of various solid tumor cancers (including but not limited to colorectal cancer, breast cancer, lung cancer, and liver cancer) and hematological malignancies. In some embodiments disclosed herein, the dual-specific bifunctional polypeptide comprises a second targeting moiety that is capable of binding to PCNA. Some examples of targeting moieties that target PCNA include those listed in Table 28 listed as targeting PCNA. In some embodiments, other suitable PCNA targeting moieties generally known in the art are used. The dual-specific bifunctional polypeptides disclosed herein comprising a second targeting moiety targeting PCNA may be used for the treatment of a cancer, for example, solid tumor cancers (including but not limited to colorectal cancer, breast cancer, lung cancer, and liver cancer) and hematological malignancies. In some embodiments, the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting PCNA comprises a localization peptide sequence which directs the dual-specific bifunctional polypeptide to the nucleus of a cell. In some embodiments, the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequences of MYC, SPOP, Hrp1, SV40, 53BP1, and nucleoplasmin. In some embodiments, the localization peptide sequence comprises or consists of a NLS sequence selected from the group of the NLS sequence of MYC, optionally mcyNLS and / or 3xmycNLS, SPOP, Hrp1, SV40, optionally svNLS or 3xsvNLS, and nucleoplasmin. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 114-127. In some embodiments, the NLS comprises or consists of a sequence selected from any one of SEQ ID NOs: 115-116 and 118-122. In some embodiments, the dual-specific bifunctional polypeptide comprising a second targeting moiety targeting PCNA comprises a URD derived from a URD selected from the group consisting of DCAF1, NHLRC1, RNF125, or SPOP. In some embodiments, the URD comprises or consists of DCAF1.1, NHLRC1.1, RNF125.2, RNF125.3, RNF125.4, RNF125.5, RNF125.6, SPOP.2 or SPOP.3. In some embodiments, the URD comprises or consists of optionally NHLRC1.1 or RNF125.2. In some embodiments, the URD is truncation or fragment thereof that retains ubiquitin-proteasome recruiting activity. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 39-113. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 55, 73, 74, 76 and 88-92. In some embodiments, the URD comprises or consists of a sequence selected from any one of SEQ ID NOs: 76 and 88. In some embodiments, the dual-specific bifunctional polypeptide targeting PCNA comprises a second targeting moiety that comprises or consists of a targeting moiety disclosed in Table 28 as targeting PCNA. In some embodiments, the second targeting moiety binds, or binds at least in part, to at least a portion of amino acids 38-48, 123-129, or 251-257 or any combination thereof, of PCNA (SEQ ID NO: 3). In some embodiments, the second targeting moiety comprises or consists of an endogenous protein binding partner of the target protein, a fragment and / or a derivative thereof. In some embodiments, the second targeting moiety comprises or consists of con1, con1.1, con1.2, p21, p21.1, p21.2, p21.3, p21.4, p21.5, p21.6, p21.7, p21.8, p21.9, or a fragment thereof that is capable of binding to the target protein. In some embodiments, the second targeting moiety does not comprise full length or unmodified con1 or p21. In some embodiments, the second targeting moiety comprises or consists of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 334- 344. In some embodiments where the amino acid sequence differs from a recited reference sequence, the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments of the dual-specific bifunctional polypeptide targeting PCNA the URD is not derived from SPOP. In some embodiments, the URD does not comprise or consist of SPOP.1, SPOP.2, or SPOP.3. In some embodiments, the URD does not comprise or consist of a sequence selected from any one of SEQ ID NOs: 72-74. In some embodiments, disclosed herein is a polynucleotide encoding any of the dual- specific bifunctional polypeptides targeting Myc and PCNA disclosed above, or elsewhere herein. Additional Structural Features of the Bispecific Polypeptides The following features may be generally applicable to the disclosed embodiments of the bifunctional polypeptides and dual-specific bifunctional polypeptides herein. Linker Peptides In some embodiments, the bifunctional polypeptide or the dual-specific bifunctional polypeptide disclosed above and herein further comprise one or more linker peptides. In some embodiments, the linker peptide is a length that allows for ubiquitination of the target protein via the URD when the target protein is bound by the first and / or second targeting moiety. Any suitable linker peptide generally known in the art may be used in embodiments herein. In some embodiments, the linker peptide is positioned between one or more of: the first and the second targeting moieties; the first and / or second targeting moiety and the URD; the NLS and the first and / or second targeting moiety; the NLS and the URD; and / or the NLS and an epitope tag, optionally an HA tag. In some embodiments, the linker peptide is positioned between the first and / or second targeting moiety and the URD. In some embodiments, the linker peptide is 0 (i.e., there is no linker), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 amino acids in length, or a range defined by any two of the preceding values. In some embodiments, the linker peptide is 0-30, 1-30, 2-30, 0-20, 1-20, 2- 20, 0-15, 0-12, 0-10, 1-15, 1-12, 1-10, 2-15, 2-12, 2-10, 3-15, 3-12, or 3-10 amino acids in length, optionally 2-30 amino acids in length. In some embodiments, the linker peptide comprises or consists of glycine and serine. In some embodiments, the linker peptide comprises or consists of one or more alpha helixes, optionally flanked by one or more glycine and / or a serine residues. In some embodiments, the linker peptide comprises or consists of the amino acid sequence of any one of SEQ ID NOs: 345-383. In some embodiments, the linker peptide comprises or consists of the amino acid sequence of any one of SEQ ID NOs: 347-352. Note that in the sequence listing submitted herewith, SEQ ID NO: 352 is blank because the sequence listing rules do not permit an amino acid sequence of fewer than four specifically defined amino acids, and the sequence of SEQ ID NO: 352 is “GS,” which is only two amino acids long. Therefore, “SEQ ID NO: 352” can be replaced with “GS” herein. For the same reason, SEQ ID NOs: 345-383 is the same as SEQ ID NOs: 345-351, GS, and 353-383. Likewise, SEQ ID NOs: 347-352 is the same as SEQ ID NOs: 347-351 and GS. Exemplary linker sequences are disclosed in Table 32.

[0002] Table 32: Exemplary linker sequences Orientation of Elements of Polypeptides In some embodiments, the bifunctional polypeptide or the dual-specific bifunctional polypeptide disclosed above and herein comprises a first targeting moiety, an optional second targeting moiety, and a URD. The orientation of the URD and SRD of exemplary proteins from which URDs can be derived is provided in Table 23, with “URD-SRD” indicating the URD is upstream of the SRD, and “SRD-URD” indicating the SRD is upstream of the URD, when viewed in the standard N- to C-terminal direction. In some embodiments, the orientation of the first and / or second targeting moiety relative to the URD is the same orientation as compared to the naturally occurring substrate recognition domain (SRD) of the protein from which the URD is derived. In some embodiments, the orientation of the first and / or second targeting moiety relative to the URD is the opposite orientation as compared to the naturally occurring substrate recognition domain of the protein from which the URD is derived. In some embodiments, the first and / or second targeting moiety is N-terminal relative to the URD. In some embodiments, the first and / or second targeting moiety is C-terminal relative to the URD. In some embodiments of a dual-specific bifunctional polypeptide, both the first and the second targeting moiety are N-terminal relative to the URD. In some embodiments, a dual-specific bifunctional polypeptide, both the first and the second targeting moiety are C-terminal relative to the URD. Tag peptides In some embodiments, the bifunctional polypeptide or the dual-specific bifunctional polypeptide disclosed above and herein further comprises an epitope tag. In some embodiments, the epitope tag is a hemagglutinin (HA) tag. In some embodiments, the HA tag comprises or consists of the amino acid sequence of SEQ ID NO: 384. In some embodiments, the bifunctional polypeptide or dual-specific bifunctional polypeptide does not comprise an epitope tag. In some embodiments, the bifunctional polypeptide or dual-specific bifunctional polypeptide does not comprise a hemagglutinin (HA) tag. In some embodiments, the bifunctional polypeptide or dual-specific bifunctional polypeptide does not comprise an HA tag comprising or consisting of the amino acid sequence of SEQ ID NO: 384. In some embodiments, the epitope tag can be used to visualize the bifunctional polypeptide or dual- specific bifunctional polypeptide. Typically, bifunctional polypeptides or dual-specific bifunctional polypeptides comprising an epitope tag will be used for experimentation and visualization purposes. In some embodiments, the bifunctional polypeptide or dual-specific bifunctional polypeptides intended for treatment do not have an epitope tag. In some embodiments, the bifunctional polypeptide or dual-specific bifunctional polypeptides intended for treatment have an epitope tag. Overall size of the bifunctional and dual-specific bifunctional polypeptides In some embodiments, the bifunctional polypeptide is less than or equal to 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 amino acids long, or a range defined by any two of the preceding values, optionally 50-800, 50-650, 50-500, 50-400, 70-800, 70-650, 70-500, 70-400, 70-300, 70-200, 80-800, 80-650, 80-500, 80-400, 80-300, or 80-200 amino acids long, optionally 90-550, 150-550, or 80-450 amino acids long. In some embodiments, the dual- specific bifunctional polypeptide is, is about, is at least, is at least about, is not more than, or is not more than about, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950. 1000, 1050, 1100, or 1150 amino acids long, or a range defined by any two of the preceding values, for example, 60-1150 amino acids, 60-800 amino acids, 60-400 amino acids, 400-1150 amino acids, 400- 800 amino acids, 600-1150 amino acids, or 100-700 amino acids long, optionally 120-400 or 130-370 amino acids long. Binding characteristics In some embodiments, the first and / or second targeting moiety and / or dual-specific bifunctional polypeptide of the present disclosure have an equilibrium dissociation constant (Kd) of less (that is superior binding) than about 10-7or 10-8M, for example, less than about 10-9M or 10-10M, in some embodiments, less than about 10-11M, 10-12M, or 10-13M. In some embodiments, the first and / or second targeting moiety comprises or consists of a sdAb that has a Kd value of less than 1x10-7and optionally at least 1x10-10. In some embodiments, the Kd is 1.22E-07to 9.47E-09. In some embodiments, the first and / or second targeting moiety and / or dual-specific bifunctional polypeptide of the present disclosure have an association rate constant of at least (that is superior binding rate) about 10+2or 10+31 / Ms, for example, at least about 10+51 / Ms or 10+61 / Ms, in some embodiments, at least about 10+71 / Ms, 10+81 / Ms, or 10+91 / Ms. In some embodiments, the first and / or second targeting moiety comprises or consists of a sdAb that has a kon value of at least 1x10+41 / Ms and optionally at least 1x10+51 / Ms, optionally wherein the konis 6.79E+041 / Ms to 4.04E+051 / Ms. In some embodiments, the first and / or second targeting moiety and / or dual-specific bifunctional polypeptide of the present disclosure have a dissociation rate constant of less (that is superior binding) than about 10-1or 10-21 / s, for example, less than about 10-31 / s or 10-51 / s, in some embodiments, less than about 10-61 / s, 10-71 / s, or 10-81 / s. In some embodiments, the first and / or second targeting moiety comprises or consists of a sdAb that has a koff value of less than 1x10-2and optionally less than 1x10-4, optionally wherein the koff is 1.74E-02to 8.67E-04. In some embodiments, any of the preceding values (e.g., Kd, kon, koff) is calculated using human c-Myc, optionally as described for values of Octet sdAb Kd Human Myc Peptide Monovalent (M) in Example 4. In some embodiments, first and / or second targeting moiety and / or dual-specific bifunctional polypeptide has Kd, kon, and / or koffvalue selected from a value in Table 36, or a range defined by any two of the values presented therein for a given parameter. In some embodiments, the first and / or second targeting moiety binds selectively to the target protein. In some embodiments, the first and / or second targeting moiety binds specifically to the target protein. Exemplary Polypeptides Defined by Sequence Disclosed herein are embodiments of polypeptides comprising or consisting of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, and 385-577. In some embodiments, the polypeptide or dual-specific bifunctional polypeptide is a non-natural polypeptide. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. Modifications In some embodiments of the polypeptide or dual-specific bifunctional polypeptide disclosed herein wherein the amino acid sequence differs from the recited reference sequence the difference is the result of the inclusion of one or more modifications relative to the reference sequence. In some embodiments, the one or more modifications comprise a substitution, insertion and / or deletion. In some embodiments, the substitution is a conservative substitution. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. Exemplary Polynucleotides Also disclosed herein in some embodiments, are polynucleotides encoding for a polypeptide having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any of polypeptides, anti-Myc sdAbs, bifunctional polypeptides, or the dual-specific bifunctional polypeptides disclosed herein. In some embodiments, the polynucleotide is a DNA or an RNA. In some embodiments, the RNA is an mRNA or a circular RNA. In some embodiments, the polynucleotide is packaged in a lipid nanoparticle or a viral vector. In some embodiments, the viral vector is an adenovirus, adeno-associated virus, lentivirus, or retrovirus vector. In some embodiments, the % sequence identity is calculated over the entirety of the reference sequence. In some embodiments, the DNA the RNA, mRNA or circular RNA comprises one or more modified nucleosides. In some embodiments, up to 100% of the nucleotides comprising uracil are replaced with pseudouridine and / or N1-methylpseudouridine. In some embodiments, the polynucleotide is packaged in a lipid nanoparticle, a polymeric nanoparticle, an extracellular vesicle, optionally an exosome, or a viral vector, optionally a replicating viral vector or a non-replicating viral vector, optionally an adenovirus, adeno-associated virus, lentivirus, or retrovirus vector. Methods of making lipid nanoparticles for RNA delivery are known in the art. In some embodiments, the lipid nanoparticle is made from: an ionizable cationic lipid, a PEGylated lipid, a phospholipid, and cholesterol. In some embodiments, a neutral ionizable amino lipid is used. Lipid nanoparticles for RNA delivery are disclosed in, for example: US11338044B2; US20180153822A1; US20220249699A1; WO2022251953A1; Mitchell et al., “Engineering precision nanoparticles for drug delivery,” Nature Rev. Drug Discovery (2021) 20:101-124; Kulkarni et al., “Lipid Nanoparticles Enabling Gene Therapies: From Concepts to Clinical Utility,” Nucleic Acid Therapeutics (2018) 28(3):146-157; Hou et al. “Lipid nanoparticles for mRNA delivery,” Nature Reviews Materials (2021) 6:1078-1094; each of which is incorporated herein by reference in its entirety. Exemplary Pharmaceutical Compositions, Uses, and Methods Also disclosed herein in some embodiments are pharmaceutical compositions comprising any of the polypeptides, anti-Myc sdAbs, bifunctional polypeptides, dual-specific bifunctional polypeptides and / or the polynucleotides disclosed herein and one or more pharmaceutically acceptable excipients, carriers, or diluents. Disclosed herein are pharmaceutical compositions comprising any of the polypeptides, anti-Myc sdAbs, bifunctional polypeptides, dual-specific bifunctional polypeptides and / or the polynucleotides disclosed herein and one or more pharmaceutically acceptable excipients, carriers, or diluents. In some embodiments, the composition is formulated for intravenous, intraperitoneal, intra- arterial, subcutaneous, intramuscular, intrathecal, intratumoral, inhalation, or intracranial administration. In some embodiments, the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition disclosed herein is for use in the treatment of a cancer in a patient in need thereof. In some embodiments, the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition disclosed herein is for use in the manufacture of a medicament. In some embodiments, the medicament is for the treatment of cancer. Disclosed herein in some embodiments, is a method of treating a subject comprising administering the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition disclosed herein to a subject in need thereof. In some embodiments, the subject has a cancer. Disclosed herein in some embodiments, is a method of reducing the amount of a target protein in a cell comprising contacting the cell with the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition disclosed herein. In some embodiments, the target protein is selected from Myc, (optionally c-Myc), CTNNB1, and / or PCNA. In some embodiments, the cell is in a subject, and the contacting comprises administering the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition to the subject. In some embodiments, the subject has cancer. In some embodiments, the administering is intravenous, intraperitoneal, intra-arterial, subcutaneous, intramuscular, intrathecal, intra-tumoral, or intracranial administration. In some embodiments, the cell is ex vivo, and said contacting comprises contacting the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition to the cell ex vivo, optionally in an adoptive cell therapy. In some embodiments, the method further comprises administering the cell to a subject after the contacting step, optionally wherein the subject is also the source of the cell. In some embodiments, in the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition or method disclosed herein the bifunctional polypeptide, or dual-specific bifunctional polypeptide promotes proteasome-mediated degradation of a target protein when measured in one or more assays described in and Exemplary Assay for assessing proteasomal-mediated degradation of target protein disclosed herein. In some embodiments, the assay is a HiBiT™ tag assay. In some embodiments, the assay is a Western blot, optionally wherein the proteasome-mediated degradation is inhibited when the cells comprising the target protein and the bifunctional polypeptide or dual-specific bifunctional polypeptide are treated with a proteasome inhibitor. In some embodiments, the treatment with the proteasome inhibitor reduces the amount of degradation of the target protein by at least 50%, 60%, 70%, 80%, 90%, 95% or 100% as compared to cells not treated with the proteasome inhibitor. Exemplary Assays for assessing proteasomal-mediated degradation of target protein(s) The following is an embodiment of exemplary assays for determining if a bifunctional polypeptide or dual-specific bifunctional polypeptide promotes proteasomal-mediated degradation of a target protein(s) and therefore that the URD retains ubiquitin-proteasome recruiting activity, and / or that the targeting moiety binds the target protein. As used herein, a URD is a domain derived from a ubiquitin-proteasome system component that has the physical property of recruiting the ubiquitin-proteasome system machinery and the functional property of enabling the polyubiquitination and degradation of the recruited target(s) of interest. In an exemplary screening assay, the target(s) of interest (either endogenous and / or exogenous target) is engineered to harbor the HiBiT™ tag (Promega) in a relevant cell line. The cell line is transfected with a plasmid encoding the bifunctional polypeptide, optionally dual-specific, designed to promote proteasome-mediated degradation of the target(s) of interest. 24 hours post transfection, doxycycline is added to induce expression of the bifunctional polypeptide. The HiBiT™ assay is performed the next day according to manufacturer instructions. Loss of HiBiT™ signal is indicative that the bifunctional polypeptide promotes proteasome-mediated degradation of the target(s), and that the URD retains ubiquitin-proteasome recruiting activity and / or that the targeting moiety binds the target. A construct that leads to loss of HiBiT™ signal can be subjected to further confirmation in the assay described below. Additional information regarding the HiBiT™ system can be found in Dixon et al. NanoLuc Complementation Reporter Optimized for Accurate Measurement of Protein Interactions in Cells. ACS Chem Biol. (2016) 11(2):400-8, which is hereby expressly incorporated by reference in its entirety. An exemplary assay for confirmation of proteasome-mediated degradation activity of the bifunctional polypeptide, optionally dual-specific, is described. This assay can be used in addition to the assay described above, or independent of the above assay. After a suitable time to allow proteasome-mediated degradation of the target(s) of interest (e.g., 24 to 72 hours), lysate of cells expressing the target(s) of interest and the bifunctional polypeptide of interest, and control cells that express the target(s) of interest but not the bifunctional polypeptide of interest, are subjected to SDS-PAGE, transferred onto a suitable membrane, and probed with antibodies that are specific and selective for the target(s) of interest (Western Blot). Loss of target protein is indicative that the bifunctional polypeptide promotes proteasome-mediated degradation of the target, and that the URD retains ubiquitin-proteasome recruiting activity. In some embodiments, to demonstrate that the target loss is proteasome dependent, cells expressing the target and the bifunctional polypeptide of interest are treated with a proteasome inhibitor such as bortezomib, MG-132, or lactacystin. The cells expressing the target(s) and the bifunctional polypeptide of interest in the presence of the proteasome inhibitor will show a partial (e.g., at least 50%, 60%, 70%, 80%, 90%, or 95%) or total (100%) reduction in amount of degradation as compared to cells not treated with the proteasome inhibitor, which indicates that the loss of the target is proteasome-dependent, which is indicative that the bifunctional polypeptide promotes proteasome-mediated degradation of the target(s), and that the URD retains ubiquitin-proteasome recruiting activity. For example, if the cells expressing the target(s) and the bifunctional polypeptide of interest in the absence of a proteasome inhibitor reduce the target protein by 90% relative to control cells that express the target(s) of interest but not the bifunctional polypeptide of interest, but only by 9% in the presence of a proteasome inhibitor, the proteasome inhibitor reduced the amount of degradation by 90% ((90%-9%) / 90% = 90%). Additional target proteins, target binding domains, linker sequences, and other disclosures related to components, features, uses, etc. of bispecific polypeptides are disclosed in PCT / US2023 / 066619, filed May 4, 2023, and PCT / US2023 / 76886, filed October 13, 2023, each of which is herein incorporated by reference in its entirety. Terms In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which the claimed subject matter belongs when read in light of the current disclosure. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of any subject matter claimed. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. The articles “a” and “an” are used herein to refer to one or to more than one (for example, at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. By “about” is meant a quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length that is approximately the recited value, which can vary by as much as 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1% of the recited value. Where it is not clear from the context what is encompassed by “about,” it will mean the value recited + / - 10%. Throughout this specification, unless the context requires otherwise, the words “comprise,” “comprises,” and “comprising” will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements. By “consisting of” is meant including, and limited to, whatever follows the phrase “consisting of.” Thus, the phrase “consisting of” indicates that the listed elements are required or mandatory, and that no other elements may be present. By “consisting essentially of” is meant including any elements listed after the phrase and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase “consisting essentially of” indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they materially affect the activity or action of the listed elements. The terms “individual”, “subject”, or “patient” as used herein have their plain and ordinary meaning as understood in light of the specification, and mean a human or a non-human mammal, e.g., a dog, a cat, a mouse, a rat, a cow, a sheep, a pig, a goat, a non-human primate, or a bird, e.g., a chicken, as well as any other vertebrate or invertebrate. The term “mammal” is used in its usual biological sense. Thus, it specifically includes, but is not limited to, primates, including simians (chimpanzees, apes, monkeys) and humans, cattle, horses, sheep, goats, swine, rabbits, dogs, cats, rodents, rats, mice, guinea pigs, or the like. As used herein, the term “isolated” has its plain and ordinary meaning as understood in light of the specification, and refers to a substance and / or entity that has been (1) separated from at least some of the components with which it was associated when initially produced (whether in nature and / or in an experimental setting), and / or (2) produced, prepared, and / or manufactured by the hand of man. Isolated substances and / or entities may be separated from equal to, about, at least, at least about, not more than, or not more than about, 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, about 98%, about 99%, substantially 100%, or 100% of the other components with which they were initially associated (or ranges including and / or spanning the aforementioned values). In some embodiments, isolated agents are, are about, are at least, are at least about, are not more than, or are not more than about 80%, about 85%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99%, substantially 100%, or 100% pure (or ranges including and / or spanning the aforementioned values). As used herein, a substance that is “isolated” may be “pure” (e.g., substantially free of other components). As used herein, the term “isolated cell” may refer to a cell not contained in a multi-cellular organism or tissue. As used herein, “in vivo” is given its plain and ordinary meaning as understood in light of the specification and refers to the performance of a method inside living organisms, usually animals, mammals, including humans, and plants, as opposed to a tissue extract or dead organism. As used herein, “ex vivo” is given its plain and ordinary meaning as understood in light of the specification and refers to the performance of a method outside a living organism with little alteration of natural conditions. As used herein, “in vitro” is given its plain and ordinary meaning as understood in light of the specification and refers to the performance of a method outside of biological conditions, e.g., in a petri dish or test tube. The terms “nucleic acid” or “nucleic acid molecule” as used herein have their plain and ordinary meaning as understood in light of the specification, and refer to polynucleotides, such as deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), oligonucleotides, those that appear in a cell naturally, fragments generated by the polymerase chain reaction (PCR), and fragments generated by any of ligation, scission, endonuclease action, and exonuclease action. Nucleic acid molecules can be composed of monomers that are naturally occurring nucleotides (such as DNA and RNA), or analogs of naturally occurring nucleotides (e.g., enantiomeric forms of naturally occurring nucleotides), or a combination of both. Modified nucleotides can have alterations in sugar moieties and / or in pyrimidine or purine base moieties. Sugar modifications include, for example, replacement of one or more hydroxyl groups with halogens, alkyl groups, amines, and azido groups, or sugars can be functionalized as ethers or esters. Moreover, the entire sugar moiety can be replaced with sterically and electronically similar structures, such as aza-sugars and carbocyclic sugar analogs. Examples of modifications in a base moiety include alkylated purines and pyrimidines, acylated purines or pyrimidines, or other well-known heterocyclic substitutes. Nucleic acid monomers can be linked by phosphodiester bonds or analogs of such linkages. Analogs of phosphodiester linkages include phosphorothioate, phosphorodithioate, phosphoroselenoate, phosphorodiselenoate, phosphoroanilothioate, phosphoranilidate, or phosphoramidate. The term “nucleic acid molecule” also includes so-called “peptide nucleic acids,” which comprise naturally occurring or modified nucleic acid bases attached to a polyamide backbone. Nucleic acids can be either single stranded or double stranded. “Oligonucleotide” can be used interchangeable with nucleic acid and can refer to either double stranded or single stranded DNA or RNA. A nucleic acid or nucleic acids can be contained in a nucleic acid vector or nucleic acid construct (e.g., plasmid, virus, retrovirus, lentivirus, bacteriophage, cosmid, fosmid, phagemid, bacterial artificial chromosome (BAC), yeast artificial chromosome (YAC), or human artificial chromosome (HAC)) that can be used for amplification and / or expression of the nucleic acid or nucleic acids in various biological systems. Typically, the vector or construct will also contain elements including but not limited to promoters, enhancers, terminators, inducers, ribosome binding sites, translation initiation sites, start codons, stop codons, polyadenylation signals, origins of replication, cloning sites, multiple cloning sites, restriction enzyme sites, epitopes, reporter genes, selection markers, antibiotic selection markers, targeting sequences, peptide purification tags, or accessory genes, or any combination thereof. A nucleic acid or nucleic acid molecule can comprise one or more sequences encoding different peptides, polypeptides, or proteins. These one or more sequences can be joined in the same nucleic acid or nucleic acid molecule adjacently, or with extra nucleic acids in between, e.g. linkers, repeats or restriction enzyme sites, or any other sequence that is, is about, is at least, is at least about, is not more than, or is not more than about, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, or 300 bases long, or any length in a range defined by any two of the aforementioned lengths. The term “downstream” on a nucleic acid as used herein has its plain and ordinary meaning as understood in light of the specification and refers to a sequence being after the 3’-end of a previous sequence, on the strand containing the encoding sequence (sense strand) if the nucleic acid is double stranded. The term “upstream” on a nucleic acid as used herein has its plain and ordinary meaning as understood in light of the specification and refers to a sequence being before the 5’-end of a subsequent sequence, on the strand containing the encoding sequence (sense strand) if the nucleic acid is double stranded. The term “grouped” on a nucleic acid as used herein has its plain and ordinary meaning as understood in light of the specification and refers to two or more sequences that occur in proximity either directly or with extra nucleic acids in between, e.g. linkers, repeats, or restriction enzyme sites, or any other sequence that is, is about, is at least, is at least about, is not more than, or is not more than about, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, or 300 bases long, or any length in a range defined by any two of the aforementioned lengths, but generally not with a sequence in between that encodes for a functioning or catalytic polypeptide, protein, or protein domain. The nucleic acids described herein comprise nucleobases. Primary, canonical, natural, or unmodified bases are adenine, cytosine, guanine, thymine, and uracil. Other nucleobases include but are not limited to purines, pyrimidines, modified nucleobases, 5-methylcytosine, pseudouridine, dihydrouridine, inosine, 7-methylguanosine, hypoxanthine, xanthine, 5,6- dihydrouracil, 5-hydroxymethylcytosine, 5-bromouracil, isoguanine, isocytosine, aminoallyl bases, dye-labeled bases, fluorescent bases, or biotin-labeled bases. In some embodiments, the uridine of the RNA, mRNA or circular RNA is pseudouridine. In some embodiments, the uridine of the RNA, mRNA or circular RNA is N1-methylpseudouridine. In some embodiments, the uracil of the RNA, mRNA or circular RNA is a mixture of pseudouridine and N1-methylpseudouridine. In some embodiments, up to 100% of the nucleotides comprising uracil are replaced with pseudouridine and / or N1-methylpseudouridine. The terms “peptide”, “polypeptide”, and “protein” as used herein have their plain and ordinary meaning as understood in light of the specification and refer to macromolecules comprised of amino acids linked by peptide bonds. The numerous functions of peptides, polypeptides, and proteins are known in the art, and include but are not limited to enzymes, structure, transport, defense, hormones, or signaling. Peptides, polypeptides, and proteins are often, but not always, produced biologically by a ribosomal complex using a nucleic acid template, although chemical syntheses are also available. By manipulating the nucleic acid template, peptide, polypeptide, and protein mutations such as substitutions, deletions, truncations, additions, duplications, or fusions of more than one peptide, polypeptide, or protein can be performed. These fusions of more than one peptide, polypeptide, or protein can be joined in the same molecule adjacently, or with extra amino acids in between, e.g. linkers, repeats, epitopes, or tags, or any other sequence that is, is about, is at least, is at least about, is not more than, or is not more than about, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, or 300 bases long, or any length in a range defined by any two of the aforementioned lengths. The term “downstream” on a polypeptide as used herein has its plain and ordinary meaning as understood in light of the specification and refers to a sequence being after the C-terminus of a previous sequence. The term “upstream” on a polypeptide as used herein has its plain and ordinary meaning as understood in light of the specification and refers to a sequence being before the N-terminus of a subsequent sequence. A polypeptide or amino acid sequence “derived from” a designated protein refers to the origin of the polypeptide. Preferably, the polypeptide has an amino acid sequence that is essentially identical to that of a polypeptide encoded in the sequence, or a portion thereof, or which is immunologically identifiable with a polypeptide encoded in the sequence. This terminology also includes a polypeptide expressed from a designated nucleic acid sequence. Peptide sequences having at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% homology to any one of the peptide sequences disclosed herein and having the same or similar functional properties are envisioned. The percent homology may be determined according to amino acid substitutions, deletions, or additions between two peptide sequences. Peptide sequences having some percent homology to any one of the peptide sequences disclosed herein may be produced and tested by one skilled in the art through conventional methods. The term “artificial” or “non-natural” denotes that the polypeptide or portion of a polypeptide in question has a sequence that is not present, in the noted state, in nature. In the present context the polypeptides have been altered from their native state, so that their sequences are no longer those found in wild-type proteins. Where a portion derived from a naturally occurring protein (e.g., a URD or NLS) is a fragment of the naturally occurring protein which does not contain an altered sequence (other than being less than the complete sequence of the naturally occurring protein), a “non-natural” polypeptide comprising the derived portion does not encompass the naturally occurring protein from which the portion is derived. That is to say that a “non-natural” polypeptide comprising the portion must contain additional amino acids which are not found in the natural protein. As disclosed herein, sequences having a % identity to any of the sequences disclosed herein are envisioned and may be used. The terms “% identity” refer to the percentage of units (i.e., amino acids or nucleotides) that are the same between two or more sequences relative to the length of the sequence. When the two or more sequences being compared are the same length, the % identity will be respective to that length. When two or more sequences being compared are different lengths, deletions and / or insertions may be introduced to obtain the best alignment. In some embodiments, these sequences may include peptide sequences, nucleic acid sequences, CDR sequences, variable region sequences, or heavy or light chain sequences. In some embodiments, any sequence having at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any of the sequences disclosed herein may be used. In some embodiments, any sequence having at least 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 substitutions, deletions, or additions relative to any of the sequences disclosed herein may be used. The changes in sequences may apply to, for example, single amino acids, single nucleic acid bases, or nucleic acid codons; however, differences in longer stretches of sequences are also envisioned. As applied to sequences associated with antibodies or binding regions thereof, these differences in sequences may apply to antigen-binding regions (e.g., CDRs) or regions that do not bind to antigens or are only secondary to antigen binding (e.g., framework regions). As disclosed herein, sequences having a % homology to any of the sequences disclosed herein are envisioned and may be used. The term “% homology” refers to the degree of conservation between two sequences when considering their three-dimensional structure. For example, homology between two protein sequences may be dependent on structural motifs, such as beta strands, alpha helices, and other folds, as well as their distribution throughout the sequence. Homology may be determined through structural determination, either empirically or in silico. In some embodiments, any sequence having at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence homology to any of the sequences disclosed herein may be used. In some embodiments, any sequence having at least 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 substitutions, deletions, or additions relative to any of the sequences disclosed herein, which may or may not affect the overall % homology, may be used. As applied herein, sequences having a certain % similarity to any of the sequence disclosed herein are envisioned and may be used. In some embodiments, these sequences may include peptide sequences, nucleic acid sequences, CDR sequences, variable region sequences, or heavy or light chain sequences. As understood in the art with respect to peptide sequences, “similarity” refers to the comparison of amino acids based on their properties, including but not limited to size, polarity, charge, pK, aromaticity, hydrogen bonding properties, or presence of functional groups (e.g., hydroxyl, thiol, amine, carboxyl, and the like). The term “% similarity” refers to the percentage of units (e.g., amino acids) that are the same between two or more sequences relative to the length of the sequence. When the two or more sequences being compared are the same length, the % similarity will be respective that length. When two or more sequences being compared are different lengths, deletions and / or insertions may be introduced to obtain the best alignment. The similarity of two amino acids may dictate whether a certain substitution is conservative or non-conservative. Methods of determining the conservativeness of an amino acid substitution are generally known in the art and may involve substitution matrices. Commonly used substitution matrices include BLOSUM45, BLOSUM62, BLOSUM80, PAM100, PAM120, PAM160, PAM200, PAM250, but other substitution matrices or approaches may be used as considered appropriate by the skilled person. A certain substitution matrix may be preferential over the others when considering aspects such as stringency, conservation and / or divergence of related sequences (e.g., within the same species or broader), and length of the sequences in question. As used herein, a peptide sequence having a certain % similarity to another sequence will have up to that % of amino acids that are either identical or an acceptable substitution as governed by the method of similarity determination used. In some embodiments, a sequence having at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence similarity to any of the sequences disclosed herein may be used. In some embodiments, any sequence having at least 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 similar substitutions relative to any of the sequences disclosed herein may be used. As applied to sequences associated with antibodies or binding regions thereof, these similar substitutions may apply to antigen-binding regions (i.e., CDRs) or regions that do not bind to antigens or are only secondary to antigen binding (i.e., framework regions). In some embodiments, the percent identity is over the CDR and / or FR regions noted herein. In such situations, the percent identity of the CDR or FR can be identified separately from the rest of the protein or nucleic acid sequence. Thus, two CDRs or FRs can have a specified percentage of amino acid residues or nucleotides that are the same (for example, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% sequence identity over a specified region, or, when not specified, over the entire sequence of a reference sequence), while allowing for the remainder of the protein to either stay 100% identical to the comparison protein, our while also allowing the remainder of the protein to also have variation by a specified percent identity. The term “consensus sequence” as used herein with regard to sequences has its plain and ordinary meaning as understood in light of the specification, and refers to the generalized sequence representing all of the different combinations of permissible amino acids at each location of a group of sequences. A consensus sequence may provide insight into the conserved regions of related sequences where the unit (e.g., amino acid or nucleotide) is the same in most or all of the sequences, and regions that exhibit divergence between sequences. In the case of sequences associated with antibodies or binding regions thereof, the consensus sequence of a CDR may indicate amino acids that are important or dispensable for antigen binding. It is envisioned that consensus sequences may be prepared with any of the sequences provided herein, and the resultant various sequences derived from the consensus sequence can be validated to have similar effects as the template sequences. The term “purity” of any given substance, compound, or material as used herein has its plain and ordinary meaning as understood in light of the specification and refers to the actual abundance of the substance, compound, or material relative to the expected abundance. For example, the substance, compound, or material may be at least 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% pure, including all decimals in between. Pur...

Claims

WHAT IS CLAIMED IS:

1. A polypeptide comprising or consisting of an anti-Myc single domain antibody (sdAb), comprising or consisting of a VHdomain of an IgG antibody, or a VHH, or VHdomain of a heavy chain antibody (HcAb), wherein the VHor VHH domain comprises a VH CDR3 comprising or consisting of any one of SEQ ID NOs: 179, 195, 211, 219, 251, 267 or 283, optionally wherein the VH CDR3 sequence comprises 1, 2, 3, 4, 5, 6, 7, or more substitutions and / or 1, 2, 3, 4, 5, 6, 7, or more deletions or additions, and / or has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to a sequence selected from any one of SEQ ID NOs: 179, 195, 211, 219, 251, 267 and 283.

2. A polynucleotide encoding the polypeptide of claim 1, optionally wherein the polynucleotide comprises or consists of any one of SEQ ID NOs: 626-640.

3. A bifunctional polypeptide that promotes proteasome-mediated degradation of at least one target protein, the bifunctional polypeptide comprising: a) a first targeting moiety comprising or consisting of the polypeptide of claim 1, wherein the polypeptide comprises or consists of the anti-Myc sdAb; b) a ubiquitin-proteasome system recruiting domain (URD), c) optionally a first linker peptide, optionally wherein the first linker peptide is positioned between the first targeting moiety and the URD, d) optionally one or more localization peptide sequences, wherein at least one target protein is MYC, optionally c-MYC, and wherein proximity of the bifunctional polypeptide to at the least one target protein through binding of the targeting moiety induces ubiquitination of the at least one target protein via the URD, thereby promoting proteasome-mediated degradation of the at least one target protein.

4. The bifunctional polypeptide of claim 3, wherein the at least one target protein is selected from MYC, (optionally c-MYC), CTNNB1, and / or PCNA.

5. The bispecific polypeptide of claim 4, wherein the bispecific polypeptide is a dual-specific bifunctional polypeptide and wherein the second target protein comprises MYC, optionally c-MYC.

6. The bispecific polypeptide of claim 4, wherein the bispecific polypeptide is a dual-specific bifunctional polypeptide and wherein the second target protein comprises CTNNB1.

7. The bispecific polypeptide of claim 4, wherein the bispecific polypeptide is a dual-specific bifunctional polypeptide and wherein the at least one target protein comprises PCNA.

8. A polynucleotide encoding a bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of claim 3.

9. A polynucleotide encoding a bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of claim 4.

10. A polynucleotide encoding a dual-specific bifunctional polypeptide comprising or consisting of the dual-specific bifunctional polypeptide of claim 5.

11. A polynucleotide encoding a bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of claim 6.

12. A polynucleotide encoding a dual-specific bifunctional polypeptide comprising or consisting of the bifunctional polypeptide of claim 7.

13. A polypeptide comprising or consisting of an amino acid sequence having at least 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NO: 184, 192, 200, 208, 216, 224, 232, 240, 248, 256, 264, 272, 280, 288, 296, and 385-577, optionally wherein the sequence lacks the HA tag sequence (SEQ ID NO: 384).

14. A polynucleotide encoding for the polypeptide of claim 13.

15. A pharmaceutical composition comprising the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, or polynucleotide of any one of claims 1-14 and one or more pharmaceutically acceptable excipients, carriers, or diluents.

16. A method of treating a subject comprising administering the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of claims 1-14 to a subject in need thereof, optionally wherein the subject has a cancer.

17. A method of reducing the amount of a target protein in a cell comprising contacting the cell with the polypeptide comprising or consisting of the anti-Myc sdAb, bifunctional polypeptide, dual-specific bifunctional polypeptide, polypeptide, polynucleotide, or pharmaceutical composition of any one of claims 1-14, optionally wherein the target protein is selected from MYC, (optionally c-MYC), CTNNB1, and / or PCNA.

18. A compound comprising the polypeptide of claim 1, the polypeptide comprising or consisting of the anti-Myc sdAb, and a therapeutic compound and / or drug and / or detectable label conjugated to the polypeptide.

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