title: BRCA1 is phosphorylated at serine 1497 in vivo at a cyclin-dependent kinase 2 phosphorylation site.
abstract: BRCA1 is a cell cycle-regulated nuclear protein that is phosphorylated mainly on serine and to a lesser extent on threonine residues. Changes in phosphorylation occur in response to cell cycle progression and DNA damage. Specifically, BRCA1 undergoes hyperphosphorylation during late G1 and S phases of the cell cycle. Here we report that BRCA1 is phosphorylated in vivo at serine 1497 (S1497), which is part of a cyclin-dependent kinase (CDK) consensus site. S1497 can be phosphorylated in vitro by CDK2-cyclin A or E. BRCA1 coimmunoprecipitates with an endogenous serine-threonine protein kinase activity that phosphorylates S1497 in vitro. This cellular kinase activity is sensitive to transfection of a dominant negative form of CDK2 as well as the application of the CDK inhibitors p21 and butyrolactone I but not p16. Furthermore, BRCA1 coimmunoprecipitates with CDK2 and cyclin A. These results suggest that the endogenous kinase activity is composed of CDK2-cyclin complexes, at least in part, concordant with the G1/S-specific increase in BRCA1 phosphorylation.
authors.affiliation: The Salk Institute, La Jolla, California 92037, USA.
authors.forename: H
authors.initials: H
authors.lastname: Ruffner
authors.forename: W
authors.initials: W
authors.lastname: Jiang
authors.forename: A G
authors.initials: AG
authors.lastname: Craig
authors.forename: T
authors.initials: T
authors.lastname: Hunter
authors.forename: I M
authors.initials: IM
authors.lastname: Verma
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D042846:CDC2-CDC28 Kinases; D002461:Cell Line, Transformed; D019925:Cyclin A / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism
chemical_list: D019313:BRCA1 Protein; D019925:Cyclin A; D019927:Cyclin E; D013912:Threonine; D012694:Serine; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases