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E2F regulates DDB2: consequences for DNA repair in Rb-deficient cells

S Prost1, P Lu, H Caldwell

  • 1Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK. s.prost@ed.ac.uk

Oncogene
|December 19, 2006
PubMed

Insights

The DDB2 gene, crucial for DNA repair, is regulated by E2F transcription factors in mice. Loss of Rb tumor suppressor enhances DDB2 expression and DNA repair efficiency.

Area of Science:

  • Molecular Biology
  • Genetics
  • DNA Repair

Background:

  • DDB2 is implicated in global genomic repair, particularly cyclobutane pyrimidine dimer (CPD) removal, and is p53-regulated in humans.
  • DDB2's role and regulation in mouse models, especially concerning cell cycle control, remain less understood.

Purpose of the Study:

  • To investigate the transcriptional regulation of DDB2 by E2F factors in mouse epithelial cells.
  • To elucidate the impact of Retinoblastoma (Rb) protein loss on DDB2 expression and global genomic repair.
  • To determine the functional consequences of E2F-mediated DDB2 regulation on DNA repair efficiency.

Main Methods:

  • Utilized Cre-Lox technology to delete Rb in primary mouse hepatocytes.
  • Employed E2F1-antisense and E2F1-small interfering RNA (siRNA) to assess E2F1's role in DDB2 transcription.
  • Quantified DDB2 expression and CPD removal rates in Rb-null versus wild-type cells.
  • Assessed the effect of DDB2-siRNA on the DNA repair phenotype of Rb-null cells.

Main Results:

  • Mouse DDB2 expression is regulated by E2F transcription factors.
  • Deletion of Rb in hepatocytes led to increased DDB2 gene and protein expression.
  • E2F1 and E2F3 were shown to bind the DDB2 promoter, with E2F1 acting as a transcriptional regulator.
  • Rb-null cells exhibited enhanced global DNA repair and more efficient CPD removal.
  • DDB2 knockdown abolished the enhanced repair phenotype in Rb-null cells.

Conclusions:

  • Identified a novel regulatory pathway for DDB2 involving E2F transcription factors, independent of but potentiated by p53.
  • Demonstrated that DDB2 plays a significant role in global DNA repair in mouse epithelial cells.
  • Established a link between cell cycle control (Rb/E2F pathway) and DNA repair capacity via DDB2 modulation.

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