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Radiation-induced cell cycle arrest compromised by p21 deficiency

J Brugarolas1, C Chandrasekaran, J I Gordon

  • 1Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge 02139, USA.

Nature
|October 12, 1995
PubMed

Insights

The protein p21, a cell cycle inhibitor, does not affect intestinal cell differentiation or DNA damage-induced apoptosis. However, p21 deficiency impairs G1 cell cycle arrest in mouse fibroblasts after DNA damage.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • The protein p21 acts as a dual inhibitor of cyclin-dependent kinases and proliferating-cell nuclear antigen (PCNA), crucial for cell cycle progression.
  • The p21 gene is regulated by p53, suggesting a role in p53-dependent cell cycle arrest and apoptosis.
  • p21 is also linked to cellular senescence and cell cycle withdrawal during terminal differentiation.

Purpose of the Study:

  • To investigate the role of p21 in cell cycle regulation, differentiation, and apoptosis.
  • To determine the in vivo function of p21 using genetically modified mouse models.

Main Methods:

  • Utilized chimaeric mice composed of both p21 knockout (p21-/-) and wild-type (p21+/+) cells.
  • Conducted immunohistochemical analyses on adult small intestine components.
  • Assessed G1 arrest in p21-/- mouse embryo fibroblasts following DNA damage.

Main Results:

  • Deletion of p21 had no discernible impact on the differentiation of intestinal epithelial cells.
  • p21 deficiency did not affect p53-dependent apoptosis in response to irradiation.
  • p21-/- mouse embryo fibroblasts exhibited impaired G1 arrest after DNA damage.

Conclusions:

  • p21 is not essential for intestinal epithelial cell differentiation or irradiation-induced apoptosis.
  • p21 plays a critical role in facilitating G1 cell cycle arrest in response to DNA damage.
  • These findings clarify the specific functions of p21 in cell cycle control and tissue homeostasis.

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