Inhibition of cellular and SV40 DNA replication by the adeno-associated virus Rep proteins

In order to define the mechanism used by the adeno-associated virus replication (rep) gene to mediate inhibition of cell proliferation, we have studied its effects on SV40 and cellular DNA replication. SV40 DNA replication was inhibited by the presence of the rep gene in human 293 cells, and the inhibition was not linked to suppression of SV40 early gene expression. Using double-immunofluorescence assays that measured both rep gene expression and bromodeoxyuridine incorporation, we found that the presence of the Rep78 and Rep68 proteins correlated with inhibition of cellular DNA synthesis in NIH3T3 cells. This links the rep gene's anti-proliferative effects to either: (i) a direct inhibition of DNA synthesis or (ii) a possible cell cycle block.