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Control of the p53-p21CIP1 Axis by E2f1, E2f2, and E2f3 is essential for G1/S progression and cellular transformation

Nidhi Sharma1, Cynthia Timmers, Prashant Trikha

  • 1Human Cancer Genetics Program, Department of Molecular Virology, Immunology, and Medical Genetics, Comprehensive Cancer Center, Ohio State University, Columbus, Ohio 43210, USA.

The Journal of Biological Chemistry
|September 30, 2006
PubMed

Insights

The E2F1-3 transcription factors regulate cell cycle progression and oncogene-driven cell transformation. Their inactivation leads to cell cycle arrest, but loss of p53 or p21(CIP1) can restore proliferation and transformation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • The E2F family of transcription factors (E2F1-3) is crucial for regulating genes involved in cell cycle progression.
  • Previous studies indicated that E2F1-3 inactivation leads to cell cycle arrest and elevated p21(CIP1) levels.

Purpose of the Study:

  • To investigate the role of E2F1-3 in oncogene-mediated cellular transformation.
  • To elucidate the interplay between E2F1-3, p53, and p21(CIP1) in controlling cell cycle progression and transformation.

Main Methods:

  • Analysis of synchronized mouse embryonic fibroblasts deficient in E2F1-3.
  • Assessment of cell cycle progression following inactivation of p21(CIP1) or p53.
  • Evaluation of cellular transformation and tumorigenesis in E2F1-3-deficient cells.

Main Results:

  • E2F1-3 are essential for oncogene-induced transformation of mouse embryonic fibroblasts.
  • Inactivation of p21(CIP1) partially restored G1/S phase transit in E2F1-3-deficient cells.
  • Loss of p53 fully restored cell cycle progression through G1/S and mitosis, enabling transformation and tumorigenesis.
  • Inactivation of p53, but not p21(CIP1), sensitized E2F1-3-deficient cells to transformation.

Conclusions:

  • The E2F1-3 transcription factors negatively regulate the p53-p21(CIP1) axis.
  • This negative regulation by E2F1-3 is critical for normal cell cycle progression and cellular transformation.
  • Targeting the E2F1-3 pathway may offer therapeutic strategies for cancer treatment.

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