title: Inhibitory role of E2F-1 in the regulation of tumor suppressor p53 during DNA damage response.
abstract: Appropriate regulation of DNA damage response is pivotal for maintaining genome stability. p53 as well as E2F-1 plays a critical role during DNA damage response, however, the physiological significance of their interaction has been elusive. In the present study, we found that E2F-1 has an inhibitory effect on p53 during adriamycin (ADR)-mediated DNA damage response. Upon ADR exposure, p53 and E2F-1 were markedly induced at protein and mRNA levels in p53-procifient U2OS and HCT116 cells, and formed a stable complex as examined by co-immunoprecipitation experiments. Of note, chromatin immunoprecipitation (ChIP) experiments revealed that ADR-mediated induction coincides with the efficient recruitment of p53 and E2F-1 onto the promoters of p53-target genes, such as p21(WAF1) and BAX. Subsequent RT-PCR and luciferase reporter assays demonstrated that E2F-1 strongly attenuates p53-dependent transactivation of p53-target genes. Importantly, siRNA-mediated knockdown of E2F-1 stimulated apoptosis in response to ADR, which was associated with an accelerated response of p21(WAF1) and BAX. Collectively, our present findings suggest that E2F-1 participates in p53-mediated DNA damage response and might have a checkpoint function to limit overactive p53.
authors.affiliation: Laboratory of DNA Damage Signaling, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Yoshihara
authors.forename: Dan
authors.initials: D
authors.lastname: Wu
authors.forename: Natsumi
authors.initials: N
authors.lastname: Kubo
authors.forename: Meixiang
authors.initials: M
authors.lastname: Sang
authors.forename: Akira
authors.initials: A
authors.lastname: Nakagawara
authors.forename: Toshinori
authors.initials: T
authors.lastname: Ozaki
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004249:DNA Damage / Q000235:genetics*; D004317:Doxorubicin / Q000494:pharmacology; D050687:E2F1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D034741:RNA, Small Interfering / Q000235:genetics; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D004317:Doxorubicin