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Peptides containing cyclin/Cdk-nuclear localization signal motifs derived from viral initiator proteins bind to DNA

Ronald J Kim1, Stephanie Moine, Danielle K Reese

  • 1Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.

Journal of Virology
|November 5, 2002
PubMed

Insights

Phosphorylation of simian virus 40 T-antigen at Thr124 regulates DNA replication initiation. This modification reduces T-antigen

Area of Science:

  • Molecular Biology
  • Virology
  • Biochemistry

Background:

  • Simian virus 40 (SV40) DNA replication is a crucial process initiated by the viral T-antigen.
  • Regulation of T-antigen activity, particularly its assembly and DNA binding, is key to controlling viral replication.
  • Post-translational modifications, such as phosphorylation, are known to modulate protein function.

Purpose of the Study:

  • To investigate the role of phosphorylation at T-antigen residue Thr124 in regulating SV40 DNA replication.
  • To elucidate the mechanism by which phosphorylation affects T-antigen assembly and DNA binding.
  • To compare the regulatory mechanisms of SV40 T-antigen with bovine papillomavirus E1.

Main Methods:

  • Synthesis of peptides containing the nuclear localization signal (NLS) and cyclin/Cdk kinase recognition sites, centered on Thr124.
  • Assay of peptide activity in inhibiting T-antigen assembly.
  • Assessment of DNA binding properties of phosphorylated and unphosphorylated peptides.
  • Comparison with peptides derived from bovine papillomavirus E1.

Main Results:

  • Unphosphorylated "CDK/NLS" peptides inhibit T-antigen assembly and bind DNA non-specifically.
  • Phosphorylation of Thr124 significantly reduces these inhibitory and DNA-binding activities.
  • Residues within the NLS are involved in DNA binding, while the CDK motif regulates this interaction.
  • Similar regulatory patterns were observed for bovine papillomavirus E1 peptides.

Conclusions:

  • Phosphorylation of SV40 T-antigen at Thr124 is a critical regulatory event for initiating viral DNA replication.
  • The phosphorylation status of Thr124 modulates T-antigen's ability to assemble and bind DNA.
  • These findings provide insights into the control mechanisms governing viral replication initiation.

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