title: BRCA1-BARD1 complexes are required for p53Ser-15 phosphorylation and a G1/S arrest following ionizing radiation-induced DNA damage.
abstract: BRCA1 is a major player in the DNA damage response. This is evident from its loss, which causes cells to become sensitive to a wide variety of DNA damaging agents. The major BRCA1 binding partner, BARD1, is also implicated in the DNA damage response, and recent reports indicate that BRCA1 and BARD1 co-operate in this pathway. In this report, we utilized small interfering RNA to deplete BRCA1 and BARD1 to demonstrate that the BRCA1-BARD1 complex is required for ATM/ATR (ataxia-telangiectasia-mutated/ATM and Rad3-related)-mediated phosphorylation of p53(Ser-15) following IR- and UV radiation-induced DNA damage. In contrast, phosphorylation of a number of other ATM/ATR targets including H2AX, Chk2, Chk1, and c-jun does not depend on the presence of BRCA1-BARD1 complexes. Moreover, prior ATM/ATR-dependent phosphorylation of BRCA1 at Ser-1423 or Ser-1524 regulates the ability of ATM/ATR to phosphorylate p53(Ser-15) efficiently. Phosphorylation of p53(Ser-15) is necessary for an IR-induced G(1)/S arrest via transcriptional induction of the cyclin-dependent kinase inhibitor p21. Consistent with these data, repressing p53(Ser-15) phosphorylation by BRCA1-BARD1 depletion compromises p21 induction and the G(1)/S checkpoint arrest in response to IR but not UV radia-tion. These findings suggest that BRCA1-BARD1 complexes act as an adaptor to mediate ATM/ATR-directed phosphorylation of p53, influencing G(1)/S cell cycle progression after DNA damage.
authors.affiliation: Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, Brisbane, Queensland 4029, Australia.
authors.forename: Megan
authors.initials: M
authors.lastname: Fabbro
authors.forename: Kienan
authors.initials: K
authors.lastname: Savage
authors.forename: Karen
authors.initials: K
authors.lastname: Hobson
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Deans
authors.forename: Simon N
authors.initials: SN
authors.lastname: Powell
authors.forename: Grant A
authors.initials: GA
authors.lastname: McArthur
authors.forename: Kum Kum
authors.initials: KK
authors.lastname: Khanna
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004249:DNA Damage; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins; D019281:Dimerization; D016193:G1 Phase; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008954:Models, Biological; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D016196:S Phase; D012694:Serine / Q000737:chemistry; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D019313:BRCA1 Protein; D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D012694:Serine; C102449:BARD1 protein, human; D044767:Ubiquitin-Protein Ligases; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases