AMPLIFICATION MEDIATED BY POLYOMAVIRUS LARGE T-ANTIGEN DEFECTIVE IN REPLICATION

The polyomavirus large T antigen promotes homologous recombination at high rates when expressed in rat cells carrying the viral replication origin and two repeats of viral DNA sequences stably integrated into t he cellular genome. Recombination consists of both reciprocal and nonr eciprocal events and is promoted by mutants defective in the initiatio n of viral DNA synthesis (L. St-Onge, L. Bouchard, and M. Bastin, J. V irol. 67:1788-1795, 1993). We have extended our studies to a rat cell line undergoing amplification of the viral insert. We show that large T antigen promotes amplification independently of its replicative func tion but that its origin-specific DNA binding activity is not sufficie nt to promote homologous recombination.