Adenovirus-induced cyclin E activates CDK2 for virus replication

Human adenoviruses (Ads) can infect and replicate in cells at different cell-cycle stages. Ads with the E1B55K deletion preferentially replicate in cancer cells and cause oncolysis. Our laboratory has previously shown that the Ad E1b gene is involved in induction of several cell-cycle regulative genes (Rao, X. et al. Virol. 350:418--28, 2006) and that cyclin E expression is required for efficient viral replication (Zheng, X. et al. J Virol 82:3415--27, 2008). In this study, we sought to investigate the interaction of cyclin E with its partner CDK2 in Ad-infected cells. We show four lines of evidence indicating the importance of CDK2 activation by cyclin E in Ad replication. First, the replication of E1B55K-deleted Ads was partially inhibited in the transgenic CHO cell line expressing a cyclin E mutant unable to bind CDK2, but not in those expressing wild-type cyclin E or a mutant unaffecting its CDK2 binding. Second, Ad-induced cyclin E protein formed complex with CDK2, correlating with the increased phosphorylation of CDK2 at T160 and pRb at S612. Third, the CDK2 chemical inhibitor, roscovitine, decreased viral DNA synthesis, protein production, and viral yield. Finally, a siRNA specifically inhibiting CDK2 repressed the viral replication with the decrease in pRb phosphorylation. Our findings indicate that Ad-induced cyclin E activates CDK2 to target the transcription repressor pRb for Ad productive replication.