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Myc and E2F1 induce p53 through p14ARF-independent mechanisms in human fibroblasts

Mikael S Lindström1, Klas G Wiman

  • 1Department of Oncology-Pathology, Cancer Center Karolinska (CCK), R8:04, Karolinska Institutet, SE-171 76 Stockholm, Sweden.

Oncogene
|August 7, 2003
PubMed

Insights

The tumor suppressor p14ARF is not essential for Myc or E2F1-induced p53 activation and cell cycle arrest in human fibroblasts. Instead, p53 phosphorylation at Ser-15 is critical for this response.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Oncology

Background:

  • The p19ARF protein in mice is induced by oncogene activation and cellular senescence, leading to cell cycle arrest and apoptosis.
  • Human p14ARF is a tumor suppressor analogous to mouse p19ARF, regulating p53 activity.

Purpose of the Study:

  • To investigate the role of human p14ARF in regulating p53 activity in response to Myc and E2F1 activation.
  • To determine whether p14ARF is required for Myc- and E2F1-induced p53 activation and cell cycle arrest in normal human fibroblasts.

Main Methods:

  • Utilized normal human skin fibroblasts (NHFs) and WI38 lung embryonic fibroblasts.
  • Expressed conditional Myc or E2F1 estrogen receptor fusion proteins.
  • Employed short-interfering RNA (siRNA) to silence p14ARF.
  • Used caffeine, an ATM/ATR kinase inhibitor, to assess the role of p53 phosphorylation.

Main Results:

  • Both Myc and E2F1 activation rapidly induced p53 phosphorylation at Ser-15, p53 accumulation, and upregulation of p53 target genes (MDM2, p21).
  • E2F1 activation induced p14ARF, while Myc activation did not significantly increase p14ARF levels within 48 hours.
  • p53 activation and cell cycle arrest occurred even after p14ARF silencing.
  • Caffeine treatment prevented p53 accumulation, indicating the involvement of ATM/ATR kinases.

Conclusions:

  • p53 phosphorylation at Ser-15 is a major factor in the induction of p53 activity upon Myc and E2F1 activation in human fibroblasts.
  • p14ARF is not essential for the p53-mediated response to Myc and E2F1 in this cellular context.
  • The ATM/ATR-p53 signaling pathway plays a crucial role in mediating the cellular response to oncogene activation.

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