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p130/p107/p105Rb-dependent transcriptional repression during DNA-damage-induced cell-cycle exit at G2

Mark W Jackson1, Mukesh K Agarwal, Jinbo Yang

  • 1Department of Molecular Biology, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.

Journal of Cell Science
|April 14, 2005
PubMed

Insights

Normal cells stably arrest in G2 after DNA damage by repressing genes essential for mitosis. RB-family proteins, including p130 and p107, are crucial for this stable G2 arrest, unlike in tumor cells lacking p53.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • DNA damage typically halts normal cell cycle progression at the G2 phase.
  • Tumor cells with deficient p53 exhibit transient G2 arrest, eventually entering mitosis.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying stable G2 arrest in normal cells following DNA damage.
  • To elucidate the role of RB-family proteins in transcriptional repression of G2/M genes.

Main Methods:

  • Analysis of gene expression in response to DNA damage in normal and RB-family-deficient cells.
  • Assessment of cell cycle progression and DNA content using techniques like flow cytometry.
  • Evaluation of specific protein expression, including p53, p21/WAF1, p130, p107, and KI67.

Main Results:

  • DNA damage induces transcriptional repression of over 20 genes required for mitosis entry and progression.
  • RB-family proteins, particularly p130 and p107, are essential for repressing these G2/M genes.
  • Loss of RB-family proteins abrogates the stable G2 arrest, with cells failing to accumulate 4N DNA content.
  • p53-dependent downregulation of KI67 indicates cell cycle exit from G2.

Conclusions:

  • RB-family proteins mediate stable G2 arrest in normal cells by transcriptionally repressing key mitotic genes.
  • The p53-RB signaling pathway is critical for maintaining G2 arrest and preventing aberrant cell cycle re-entry after DNA damage.

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