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Negative regulation of mitotic promoting factor by the checkpoint kinase chk1 in simian virus 40 lytic infection

Eiji Okubo1, John M Lehman, Thomas D Friedrich

  • 1Center for Immunology and Microbial Disease, Albany Medical College, New York 12208, USA.

Journal of Virology
|December 28, 2002
PubMed

Insights

Simian virus 40 (SV40) infection bypasses mitosis by activating the Chk1 DNA damage checkpoint. Inhibiting Chk1 in SV40-infected cells reinitiates mitosis, revealing Chk1

Area of Science:

  • Virology
  • Cell Biology
  • Molecular Biology

Background:

  • Simian virus 40 (SV40) lytic infection in monkey kidney cells stimulates DNA synthesis, causing cells to bypass mitosis and replicate DNA beyond a 4C content.
  • Understanding the mechanisms behind this mitotic bypass is crucial for comprehending viral-induced cell cycle dysregulation.

Purpose of the Study:

  • To investigate the role of upstream regulatory molecules of mitosis-promoting factor (MPF) in SV40-induced mitotic bypass.
  • To determine if the DNA replication/damage checkpoint kinase, Chk1, is involved in the absence of mitosis during SV40 lytic infection.

Main Methods:

  • Synchronized African green monkey kidney (CV-1) cells were infected with SV40 or mock-infected.
  • Expression and phosphorylation levels of Chk1 were analyzed in G(1)/S-arrested and released cells.
  • Cells were treated with Chk1 inhibitors (UCN-01, caffeine) to assess their effect on mitosis and MPF activity.

Main Results:

  • Chk1 phosphorylation was observed in both infected and uninfected cells at G(1)/S arrest.
  • Upon release, uninfected cells lost Chk1 phosphorylation, while SV40-infected cells showed transient dephosphorylation followed by increased phosphorylation entering >G(2).
  • Inhibition of Chk1 in SV40-infected cells induced mitosis, abnormal nuclear condensation, and increased MPF activity.

Conclusions:

  • SV40 lytic infection activates components of the DNA damage checkpoint pathway, specifically involving Chk1.
  • Chk1 activity appears to contribute significantly to the suppression of mitosis during SV40 lytic infection.
  • Targeting Chk1 may offer a strategy to restore normal cell cycle progression in SV40-infected cells.

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