Cytosine base editing system and application thereof
A base editing and cytosine technology, applied in the field of cytosine base editing system, can solve the problems of limited operational range, complicated operation, low efficiency, etc., and achieve the effect of fast and efficient editing and great application potential
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Embodiment 1
[0032] Example 1 Design and construction of a cytosine base editing system based on CRISPR / Cpf1
[0033] like figure 1 As shown in A, a CRISPR / Cpf1-based cytosine editing system was constructed, which consists of the following two basic elements:
[0034] (1) A fusion protein composed of cytosine deaminase, a DNase-inactive mutant of Cpf1 (D917A) dCpf1 and a uracil glycosidase inhibitor (UGI), namely the cytosine base editor dCpf1-CBE, this fusion Proteins can bind to specific targets in the genome with the help of dCpf1, and convert cytosine (C) to thymine (T) under the action of cytosine deaminase;
[0035] Specifically, the cytosine deaminase hAPOBEC3A (GenBank: KM266646.1), hAID (GenBank: AAM95402.1) and LjCDA1L2_1 (GenBank: MG495262.1) were respectively fused to the N-terminus of dCpf1 through the XTEN short peptide linker (SGSETPGTSESATPES). , and UGI (GenBank: YP_009283008.1) was fused to the C-terminus of dCpf1 through a short peptide linker (GSPKKKRKVSGGS), and the ...
Embodiment 2
[0037] Example 2 Application of CRISPR / Cpf1-based cytosine base editing system in multi-site base editing
[0038] Validation and application of a CRISPR / Cpf1-based cytosine base editing system in Bacillus subtilis. like figure 2 shown, using IPTG-induced P grac100 The promoter expresses the cytosine base editor dCpf1-CBE in different configurations and places the crRNA array insert into the constitutive promoter P veg Afterwards, in order to realize the expression of the crRNA array, the above two expression cassettes were placed on the plasmid containing the thermosensitive replicon pE194 for base editing (C→T) in Bacillus subtilis.
[0039] Specifically, the following steps are included: the plasmid backbone used is from pJOE8999 (Altenbuchner, J., 2016. Editing of the Bacillus subtilis genome by the CRISPR-Cas9 system. Applied and Environmental Microbiology 82, 5421–5427), the plasmid was produced in E. coli and Bacillus subtilis is kanamycin resistant (KanR), and has ...
Embodiment 3
[0051]Example 3 Influence of induction time on multi-site base editing efficiency
[0052] Since the cytosine base editor containing the cytosine deaminase hAID is the most efficient, simultaneous editing of five sites can be achieved. Therefore, the effect of the induction time of IPTG on the base editing efficiency of the base editor was also investigated. As shown in Table 4, with the increase of induction time, the editing efficiency of each site increased to a certain extent, but the amplitude was limited, and the editing window did not change with the prolongation of induction time. The above results indicated that induction for 12 h was sufficient to achieve relatively complete editing. Among them, the editing and sequencing results after 36h induction are as follows image 3 shown.
[0053] Table 4 The effect of induction time on the efficiency of multi-site base editing
[0054]
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