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- Title
Poly(ADP-ribose) polymerase upregulates E2F-1 promoter activity and DNA pol α expression during early S phase.
- Authors
Simbulan-Rosenthal, Cynthia M; Rosenthal, Dean S; Luo, RuiBai; Smulson, Mark E
- Abstract
E2F-1, a transcription factor implicated in the activation of genes required for S phase such as DNA pol α, 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 α and E2F-1 expression during early S phase. To examine the role of PARP in the regulation of pol α 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 α activity assays revealed the presence of pol α 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 α expression, when quiescent cells reenter the cell cycle upon recovery from aphidicolin exposure or removal of serum.
- Subjects
DNA polymerases; PROMOTERS (Genetics); DNA replication
- Publication
Oncogene, 1999, Vol 18, Issue 36, p5015
- ISSN
0950-9232
- Publication type
Article
- DOI
10.1038/sj.onc.1202900