title: E2F1 uses the ATM signaling pathway to induce p53 and Chk2 phosphorylation and apoptosis.
abstract: The p53 tumor suppressor protein is phosphorylated and activated by several DNA damage-inducible kinases, such as ATM, and is a key effector of the DNA damage response by promoting cell cycle arrest or apoptosis. Deregulation of the Rb-E2F1 pathway also results in the activation of p53 and the promotion of apoptosis, and this contributes to the suppression of tumor development. Here, we describe a novel connection between E2F1 and the ATM DNA damage response pathway. In primary human fibroblasts lacking functional ATM, the ability of E2F1 to induce the phosphorylation of p53 and apoptosis is impaired. In contrast, ATM status has no effect on transcriptional activation of target genes or the stimulation of DNA synthesis by E2F1. Cells containing mutant Nijmegen breakage syndrome protein (NBS1), a component of the Mre11-Rad50 DNA repair complex, also have attenuated p53 phosphorylation and apoptosis in response to E2F1 expression. Moreover, E2F1 induces ATM- and NBS1-dependent phosphorylation of the checkpoint kinase Chk2 at Thr68, a phosphorylation site that stimulates Chk2 activity. Delayed gammaH2AX phosphorylation and absence of ATM autophosphorylation at Ser1981 suggest that E2F1 stimulates ATM through a unique mechanism that is distinct from agents that cause DNA double-strand breaks. These findings identify new roles for several DNA damage response factors by demonstrating that they also participate in the oncogenic stress signaling pathway between E2F1 and p53.
authors.affiliation: Department of Carcinogenesis, University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, Texas 78957, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Powers
authors.forename: SungKi
authors.initials: S
authors.lastname: Hong
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Mayhew
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Rogers
authors.forename: Erik S
authors.initials: ES
authors.lastname: Knudsen
authors.forename: David G
authors.initials: DG
authors.lastname: Johnson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins; D002110:Caffeine / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D064447:Checkpoint Kinase 2; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D006657:Histones / Q000378:metabolism; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
chemical_list: D064007:Ataxia Telangiectasia Mutated Proteins; D002110:Caffeine; D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D006657:Histones; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C493753:E2F1 protein, human; C493754:E2f1 protein, mouse; C466108:Nijmegen breakage syndrome 1 protein, mouse; C576324:ATM protein, human; C576325:Atm protein, mouse; C578634:CHEK2 protein, human; C578633:Chek2 protein, mouse; C475961:gamma-H2AX protein, mouse