Poly(ADP-ribose) polymerase upregulates E2F-1 promoter activity and DNA pol alpha expression during early S phase

Oncogene. 1999 Sep 9;18(36):5015-23. doi: 10.1038/sj.onc.1202900.


E2F-1, a transcription factor implicated in the activation of genes required for S phase such as DNA pol alpha, is regulated by interactions with Rb and by cell-cycle dependent alterations in E2F-1 abundance. We have shown that depletion of poly(ADP-ribose) polymerase (PARP) by antisense RNA expression downregulates pol alpha and E2F-1 expression during early S phase. To examine the role of PARP in the regulation of pol alpha and E2F-1 gene expression, we utilized immortalized mouse fibroblasts derived from wild-type and PARP knockout (PARP-/-) mice as well as PARP-/- cells stably transfected with PARP cDNA [PARP-/-(+PARP)]. After release from serum deprivation, wild-type and PARP-/-(+PARP) cells, but not PARP-/- cells, exhibited a peak of cells in S phase by 16 h and had progressed through the cell cycle by 22 h. Whereas [3H]thymidine incorporation remained negligible in PARP-/- cells, in vivo DNA replication maximized after 18 h in wild-type and PARP-/-(+PARP) cells. To investigate the effect of PARP on E2F-1 promoter activity, a construct containing the E2F-1 gene promoter fused to a luciferase reporter gene was transiently transfected into these cells. E2F-1 promoter activity in control and PARP-/-(+PARP) cells increased eightfold after 9 h, but not in PARP-/- cells. PARP-/- cells did not show the marked induction of E2F-1 expression during early S phase apparent in control and PARP-/-(+PARP) cells. RT - PCR analysis and pol alpha activity assays revealed the presence of pol alpha transcripts and a sixfold increase in activity in both wild-type and PARP-/-(+PARP) cells after 20 h, but not in PARP-/- cells. These results suggest that PARP plays a role in the induction of E2F-1 promoter activity, which then positively regulates both E2F-1 and pol alpha expression, when quiescent cells reenter the cell cycle upon recovery from aphidicolin exposure or removal of serum.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Carrier Proteins*
  • Cell Cycle Proteins*
  • Culture Media, Serum-Free
  • DNA Polymerase I / genetics*
  • DNA Polymerase I / metabolism
  • DNA Primers
  • DNA-Binding Proteins*
  • E2F Transcription Factors
  • E2F1 Transcription Factor
  • Mice
  • Poly(ADP-ribose) Polymerases / genetics
  • Poly(ADP-ribose) Polymerases / metabolism*
  • Promoter Regions, Genetic*
  • Retinoblastoma-Binding Protein 1
  • S Phase*
  • Transcription Factor DP1
  • Transcription Factors / genetics*
  • Up-Regulation*


  • Arid4a protein, mouse
  • Carrier Proteins
  • Cell Cycle Proteins
  • Culture Media, Serum-Free
  • DNA Primers
  • DNA-Binding Proteins
  • E2F Transcription Factors
  • E2F1 Transcription Factor
  • E2f1 protein, mouse
  • Retinoblastoma-Binding Protein 1
  • Transcription Factor DP1
  • Transcription Factors
  • Poly(ADP-ribose) Polymerases
  • DNA Polymerase I