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Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
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Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations

Published on: September 17, 2012

Cyclin B1 proteolysis via p38 MAPK signaling participates in G2 checkpoint elicited by arsenite

Ju-Pi Li1, Jia-Ling Yang

  • 1Molecular Carcinogenesis Laboratory, Institute of Biotechnology and Department of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan.

Journal of Cellular Physiology
|March 22, 2007
PubMed

Insights

p38 activation triggers cyclin B1 proteolysis, promoting the G(2) DNA damage checkpoint. Inhibiting p38 enhances cell survival and reduces genome instability by preventing premature cyclin B1 destruction.

Area of Science:

  • Cell Cycle Regulation
  • DNA Damage Response
  • Mitotic Control

Background:

  • Cyclin B1 accumulation and degradation are critical for cell cycle progression, controlling entry into and exit from mitosis.
  • DNA damage induces G(2) arrest, often involving repression of cyclin B1 transcription.
  • The role of p38 mitogen-activated protein kinase (MAPK) in regulating cyclin B1 protein levels during G(2) arrest is not fully understood.

Purpose of the Study:

  • To investigate the impact of p38 activation on cyclin B1 protein levels and its contribution to the G(2) DNA damage checkpoint.
  • To elucidate the mechanism by which p38 signaling influences cyclin B1 proteolysis.
  • To determine the functional consequences of p38-mediated cyclin B1 degradation on cell fate decisions, including apoptosis and genome stability.

Main Methods:

  • Treatment of early G(2) and asynchronous cells with arsenite to induce DNA damage and G(2) arrest.
  • Analysis of cyclin B1 protein levels, Cdk1 activation, and cell cycle progression using biochemical and cell biological techniques.
  • Investigation of the ubiquitin-proteasome pathway's role in cyclin B1 degradation.
  • Manipulation of p38 MAPK activity through inhibition or activation (e.g., MKK6-p38) and assessment of its effects on cyclin B1 ubiquitination and proteolysis.
  • Evaluation of cell viability, apoptosis, and micronucleus formation following p38 inhibition in arsenite-treated cells.

Main Results:

  • Arsenite exposure in early G(2) phase inhibited cyclin B1 accumulation and G(2)-to-M progression, but cyclin B1 remained stable in late G(2)/mitotic cells.
  • p38 activation was found to accelerate cyclin B1 proteolysis via the ubiquitin-proteasome pathway, independent of Cdc20 and Cdh1.
  • Inhibition of p38 signaling suppressed arsenite-induced cyclin B1 ubiquitination and degradation, facilitating G(2)-to-M progression and enhancing cell survival while reducing apoptosis and micronucleus formation.

Conclusions:

  • p38 MAPK signaling plays a crucial role in the G(2) DNA damage checkpoint by promoting the untimely proteolysis of cyclin B1.
  • This p38-mediated cyclin B1 degradation links G(2) arrest to downstream events such as apoptosis and potential genome instability.
  • Targeting the p38-cyclin B1 axis may offer therapeutic strategies for improving cell survival and genomic integrity in response to DNA damage.

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