Activation of SV40 DNA replication in vitro by cellular protein phosphatase 2A

D. M. Virshup, M. G. Kauffman, T. J. Kelly

Research output: Contribution to journalArticlepeer-review


We have made use of the cell-free SV40 DNA replication system to identify and characterize cellular proteins required for efficient DNA synthesis. One such protein, replication protein C (RP-C), was shown to be involved with SV40 large T antigen in the early stages of viral DNA replication in vitro. We demonstrate here that RP-C is identical to the catalytic subunit of cellular protein phosphatase 2A (PP2A(c)). The purified protein dephosphorylates specific phosphoamino acid residues in T antigen, consistent with the hypothesis that SV40 DNA replication is regulated by modulating the phosphorylation state of the viral initiator protein. We also show that purified RP-C/PP2A(c) preferentially stimulates SV40 DNA replication in extracts from early G1 phase cells. This finding suggests that the activity of a cellular factor that influences the net phosphorylation state of T antigen is cell cycle dependent.

Original languageEnglish (US)
Pages (from-to)3891-3898
Number of pages8
JournalEMBO Journal
Issue number12
StatePublished - 1989


  • T antigen
  • cell cycle regulation
  • phosphatase

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)


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