title: Checkpoint kinase 2-mediated phosphorylation of BRCA1 regulates the fidelity of nonhomologous end-joining.
abstract: The tumor suppressor gene BRCA1 maintains genomic integrity by protecting cells from the deleterious effects of DNA double-strand breaks (DSBs). Through its interactions with the checkpoint kinase 2 (Chk2) kinase and Rad51, BRCA1 promotes homologous recombination, which is typically an error-free repair process. In addition, accumulating evidence implicates BRCA1 in the regulation of nonhomologous end-joining (NHEJ), which may involve precise religation of the DSB ends if they are compatible (i.e., error-free repair) or sequence alteration upon rejoining (i.e., error-prone or mutagenic repair). However, the precise role of BRCA1 in regulating these different subtypes of NHEJ is not clear. We provide here the genetic and biochemical evidence to show that BRCA1 promotes error-free rejoining of DSBs in human breast carcinoma cells while suppressing microhomology-mediated error-prone end-joining and restricting sequence deletion at the break junction during repair. The repair spectrum in BRCA1-deficient cells was characterized by an increase in the formation of >2 kb deletions and in the usage of long microhomologies distal to the break site, compared with wild-type (WT) cells. This error-prone repair phenotype could also be revealed by disruption of the Chk2 phosphorylation site of BRCA1, or by expression of a dominant-negative kinase-dead Chk2 mutant in cells with WT BRCA1. We suggest that the differential control of NHEJ subprocesses by BRCA1, in concert with Chk2, reduces the mutagenic potential of NHEJ, thereby contributing to the prevention of familial breast cancers.
authors.affiliation: Department of Radiation Oncology, Vanderbilt University Medical Centre, 1301 22nd Avenue South, Nashville, TN 37232, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhuang
authors.forename: Junran
authors.initials: J
authors.lastname: Zhang
authors.forename: Henning
authors.initials: H
authors.lastname: Willers
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.forename: Jay H
authors.initials: JH
authors.lastname: Chung
authors.forename: Dik C
authors.initials: DC
authors.lastname: van Gent
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Hallahan
authors.forename: Simon N
authors.initials: SN
authors.lastname: Powell
authors.forename: Fen
authors.initials: F
authors.lastname: Xia
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D064447:Checkpoint Kinase 2; D004260:DNA Repair / Q000502:physiology*; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D019313:BRCA1 Protein; D004273:DNA, Neoplasm; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases