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Analysis of Cell Cycle Position in Mammalian Cells
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Analysis of Cell Cycle Position in Mammalian Cells

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Murine coronavirus nonstructural protein p28 arrests cell cycle in G0/G1 phase

Chun-Jen Chen1, Kazuo Sugiyama, Hideyuki Kubo

  • 1Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, TX 77555-1019, USA.

Journal of Virology
|September 16, 2004
PubMed

Insights

Mouse hepatitis virus (MHV) protein p28 inhibits cell proliferation by inducing G(0)/G(1) cell cycle arrest. This occurs through p53 stabilization and p21(Cip1) upregulation, preventing cell division.

Area of Science:

  • Virology
  • Molecular Biology
  • Cell Biology

Background:

  • Murine coronavirus mouse hepatitis virus (MHV) gene 1 encodes essential nonstructural proteins.
  • The specific functions of most MHV nonstructural proteins, including p28, remain largely uncharacterized.
  • p28 is encoded at the 5' end of the MHV genome.

Purpose of the Study:

  • To investigate the cellular functions of the MHV nonstructural protein p28.
  • To elucidate the mechanism by which p28 affects cell proliferation and cell cycle progression.
  • To understand the molecular interactions and pathways regulated by p28.

Main Methods:

  • Transient expression of cloned p28 in cultured cells.
  • Cell growth inhibition assays.
  • Cell cycle analysis using flow cytometry.
  • Western blot analysis to assess protein levels (pRb, p53, p21(Cip1)).
  • Analysis of mRNA transcripts for p53 and p21(Cip1).

Main Results:

  • Transient expression of p28 inhibited cell growth and suppressed cell proliferation.
  • p28 expression led to G(0)/G(1) cell cycle arrest.
  • p28 accumulated hypophosphorylated retinoblastoma protein (pRb), tumor suppressor p53, and p21(Cip1).
  • p28 increased p53 protein stability and transcriptionally upregulated p21(Cip1) in a p53-dependent manner.
  • p21(Cip1) suppressed cyclin E/Cdk2 activity, inhibiting pRb hyperphosphorylation.

Conclusions:

  • p28 induces G(0)/G(1) cell cycle arrest by stabilizing p53, leading to p21(Cip1) upregulation.
  • The accumulation of hypophosphorylated pRb, mediated by p28, blocks cell cycle progression from G(0)/G(1) to S phase.
  • p28 represents a novel viral factor that manipulates host cell cycle machinery for its own purposes.

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