Vector system for selection of genes encoding secreted proteins and membrane-bound proteins

Abstract

The subject invention concerns novel vectors for the rapid and robust selection for cDNA sequences that encode secreted or membrane-bound proteins. The invention also pertains to methods for cloning secreted or membrane-bound proteins, including proteins encoded by novel members of gene families.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application is a continuation of U.S. application Ser. No. 10 / 138,998, filed May 2, 2002, which claims the benefit of U.S. Provisional Application Ser. No. 60 / 288,046, filed May 2, 2001, each of which is hereby incorporated by reference in its entirety, including all nucleic acid sequences, amino acid sequences, figures, tables, and drawings.[0002] The subject invention was made with government support under a research project supported by National Institutes of Health Grant No. AI23338. The government may have certain rights in this invention.BACKGROUND OF THE INVENTION [0003] Proteins destined for transport into or across cell membranes are usually translated with a signal sequence that directs the newly synthesized protein to the appropriate membrane translocation system. The primary structure of signal sequences is highly variable among different proteins. Signal sequences that target proteins for export from the cytosol...

AI Technical Summary

Benefits of technology

[0014] The present invention relates to a vector system that allows rapid and robust selection for cDNA sequences that encode secreted or membrane-bound proteins. More particularly, the present invention pertains to vectors comprising a reporter gene (such as β-lactamase) lacking a functional signal sequence; a selectable marker gene (such as neomycin phosphotransferase), wherein the reporter gene and selectable marker gene are operably linked to a promoter sequence (such as the lac promoter); and a multiple cloning site. Optionally, the vectors of the subject invention can further comprise a SLIP sequence, a plurality of thymidine nucleotides that allows for all three frames of any cloned cDNA to be fused to the reporter gene, thereby increasing the efficiency of cloning cDNAs for secreted or membrane-bound proteins.

[0016] In order to improve the overall efficiency of cloning of cDNAs that encode secreted proteins or membrane-bound proteins (such as membrane-bound receptors), as well as to identify homologous genes possessing only minimal sequence relatedness, the present inventors have engineered unique plasmid-based selection vectors and developed a cloning strategy that utilizes such vectors, wherein only minimal information about the gene of interest is necessary. This cloning strategy has been validated with a number of known members of the Ig gene superfamily (IgSF) and has led to the identification of a novel V region-containing, presumably bifunctional gene in amphioxus (Branchiostoma floridae), a protochordate (cephalochordate) species that lacks an adaptive immune system.

Problems solved by technology

However, ESTs are small random cDNA sequences and thus it becomes hard to identify secretion signal sequence that is normally present in the 5′ end of cDNA encoding secreted protein.

Signal sequence trapping using mammalian cells has disadvantages, including low transfection efficiency, relatively expensive culture medium, and difficult recovery of vector-borne cDNA sequences from cells that have been transfected.

Signal sequence trapping using yeast cells also has the disadvantage of slow growth time as compared to bacterial cells.

Further, methods for molecular cloning in yeast cells are generally more complicated than bacterial methods.

It does not teach identifying signal sequences in complex eukaryotic organisms.

Further, none of the aforementioned systems incorporate a single, degenerate primer-based polymerase chain reaction (PCR) strategy designed to clone novel gene family members.

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