Polynucleotides encoding RPA4/RPA32 hybrid polypeptides

Disclosed are polynucleotides and polypeptides that are useful for assessing and modulating cell proliferation. The polynucleotides may comprise coding regions for RPA4 and RPA4/RPA32 hybrid polypeptides. The polynucleotides may be used in gene vectors for modulating cell proliferation in a patient in need thereof. Diagnostic methods related to assaying RPA4 expression in test samples in order to detect proliferating or cancerous cells also are disclosed.