Patent ID: 6866998

Claim:
A method for determining whether a test polypeptide encoded by a test nucleic acid sequence has a secretory signal region, the method comprising (a) providing a vector comprising (i) a first nucleic acid sequence encoding a portion of a translocatable protein that induces cell proliferation upon dimerization on a cell surface, wherein the portion of the translocatable protein lacks a secretory signal region present in the full-length translocatable protein; and (ii) a second nucleic acid sequence encoding a test polypeptide, wherein the second nucleic acid sequence is ligated to the first nucleic acid sequence such that expression of the vector produces a fusion protein comprising the portion of the translocatable protein and the test polypeptide; (b) introducing the vector into a host cell to produce a genetically engineered cell; (c) culturing the genetically engineered cell under conditions that permit expression of the fusion protein; and (d) detecting proliferation of the genetically engineered cell, wherein proliferation greater than that of a control cell indicates that the test polypeptide has a secretory signal region.