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Analysis of Cell Cycle Position in Mammalian Cells
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Published on: January 21, 2012

Functional availability of gamma-herpesvirus K-cyclin is regulated by cellular CDK6 and p16INK4a

Hidenori Yoshioka1, Kohji Noguchi, Kazuhiro Katayama

  • 1Division of Chemotherapy, Faculty of Pharmacy, Keio University, 1-5-30 Shiba-koen, Minato-ku, Tokyo 105-8512, Japan.

Biochemical and Biophysical Research Communications
|March 25, 2010
PubMed

Insights

Viral K-cyclin stability is regulated by CDK6 binding and p16INK4a. CDK6 binding stabilizes K-cyclin, while its absence targets it for proteasomal degradation, impacting human cell function.

Area of Science:

  • Molecular Biology
  • Virology
  • Cell Biology

Background:

  • Kaposi's sarcoma-associated herpesvirus (KSHV) encodes viral K-cyclin, homologous to mammalian D-type cyclins.
  • Understanding K-cyclin's regulatory mechanisms is crucial for comprehending viral pathogenesis and host cell cycle control.

Purpose of the Study:

  • To elucidate the regulatory mechanisms governing K-cyclin function and degradation in human cells.
  • To investigate the roles of CDK6 and p16INK4a in K-cyclin stability and activity.

Main Methods:

  • Utilized human embryonic kidney (HEK293) and primary effusion lymphoma (JSC-1) cell lines.
  • Employed proteasome inhibitor MG132 to assess K-cyclin ubiquitination and degradation.
  • Investigated the effects of CDK6 co-expression and p16INK4a silencing on K-cyclin stability and complex formation.

Main Results:

  • Proteasome inhibition (MG132) led to K-cyclin ubiquitination.
  • CDK6 co-expression prevented K-cyclin ubiquitination, stabilizing the protein.
  • K-cyclin mutants unable to bind CDK6 were degraded via the proteasome.
  • p16INK4a silencing enhanced K-cyclin-CDK6 complex formation and kinase activity.

Conclusions:

  • CDK6-bound K-cyclin is functionally stable, whereas monomeric K-cyclin undergoes ubiquitin-dependent degradation.
  • The balance between CDK6 and p16INK4a critically regulates the availability of functional K-cyclin in human cells.

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