title: Chk2 phosphorylation of BRCA1 regulates DNA double-strand break repair.
abstract: The pathway determining malignant cellular transformation, which depends upon mutation of the BRCA1 tumor suppressor gene, is poorly defined. A growing body of evidence suggests that promotion of DNA double-strand break repair by homologous recombination (HR) may be the means by which BRCA1 maintains genomic stability, while a role of BRCA1 in error-prone nonhomologous recombination (NHR) processes has just begun to be elucidated. The BRCA1 protein becomes phosphorylated in response to DNA damage, but the effects of phosphorylation on recombinational repair are unknown. In this study, we tested the hypothesis that the BRCA1-mediated regulation of recombination requires the Chk2- and ATM-dependent phosphorylation sites. We studied Rad51-dependent HR and random chromosomal integration of linearized plasmid DNA, a subtype of NHR, which we demonstrate to be dependent on the Mre11-Rad50-Nbs1 complex. Prevention of Chk2-mediated phosphorylation via mutation of the serine 988 residue of BRCA1 disrupted both the BRCA1-dependent promotion of HR and the suppression of NHR. Similar results were obtained when endogenous Chk2 kinase activity was inhibited by expression of a dominant-negative Chk2 mutant. Surprisingly, the opposing regulation of HR and NHR did not require the ATM phosphorylation sites on serines 1423 and 1524. Together, these data suggest a functional link between recombination control and breast cancer predisposition in carriers of Chk2 and BRCA1 germ line mutations. We propose a dual regulatory role for BRCA1 in maintaining genome integrity, whereby BRCA1 phosphorylation status controls the selectivity of repair events dictated by HR and error-prone NHR.
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital/Harvard Medical School, 149 13th Street, Charlestown, MA 02129, USA.
authors.forename: Junran
authors.initials: J
authors.lastname: Zhang
authors.forename: Henning
authors.initials: H
authors.lastname: Willers
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Feng
authors.forename: Jagadish C
authors.initials: JC
authors.lastname: Ghosh
authors.forename: Sang
authors.initials: S
authors.lastname: Kim
authors.forename: David T
authors.initials: DT
authors.lastname: Weaver
authors.forename: Jay H
authors.initials: JH
authors.lastname: Chung
authors.forename: Simon N
authors.initials: SN
authors.lastname: Powell
authors.forename: Fen
authors.initials: F
authors.lastname: Xia
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D064447:Checkpoint Kinase 2; D004260:DNA Repair / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D006801:Humans; D000076228:MRE11 Homologue Protein; D008954:Models, Biological; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051135:Rad51 Recombinase; D011995:Recombination, Genetic; D012694:Serine / Q000737:chemistry; D025521:Tumor Suppressor Proteins
chemical_list: D019313:BRCA1 Protein; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; C112156:NBN protein, human; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D012694:Serine; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D000076228:MRE11 Homologue Protein