Bax-mediated cell death by the Gax homeoprotein requires mitogen activation but is independent of cell cycle activity

Harris Perlman, Masataka Sata, Aude Le Roux, Thomas W. Sedlak, Didier Branellec, Kenneth Walsh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


Tissues with the highest rates of proliferation typically exhibit the highest frequencies of apoptosis, but the mechanisms that coordinate these processes are largely unknown. The homeodomain protein Gax is down-regulated when quiescent cells are stimulated to proliferate, and constitutive Gax expression inhibits cell proliferation in a p21(WAF/CIP)-dependent manner. To understand how mitogen-induced proliferation influences the apoptotic process, we investigated the effects of deregulated Gax expression on cell viability. Forced Gax expression induced apoptosis in mitogen-activated cultures, but quiescent cultures were resistant to cell death. Though mitogen activation was required for apoptosis, neither the cdk inhibitor p21(WAF/CIP) nor the tumor suppressor p53 was required for Gax-induced cell death. Arrest in G1 or S phases of the cell cycle with chemical inhibitors also did not affect apoptosis, further suggesting that Gax-mediated cell death is independent of cell cycle activity. Forced Gax expression led to Bcl-2 down-regulation and Bax up-regulation in mitogen-activated, but not quiescent cultures. Mouse embryonic fibroblasts homozygous null for the Bax gene were refractive to Gax-induced apoptosis, demonstrating the functional significance of this regulation. These data suggest that the homeostatic balance between cell growth and death can be controlled by mitogen-dependent pathways that circumvent the cell cycle to alter Bcl-2 family protein expression.

Original languageEnglish (US)
Pages (from-to)3576-3586
Number of pages11
JournalEMBO Journal
Issue number13
StatePublished - Jul 1 1998


  • Apoptosis
  • Bax
  • Cell cycle
  • Homeobox gene
  • Mitogen-regulated transcription factor

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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