title: AKT regulates BRCA1 stability in response to hormone signaling.
abstract: The observation that inherited mutations within BRCA1 result in breast and ovarian cancers suggests a functional relationship may exist between hormone signaling and BRCA1 function. We demonstrate that AKT activation promotes the expression of BRCA1 in response to estrogen and IGF-1 receptor signaling, and the rapid increase in BRCA1 protein levels appears to occur independently of new protein synthesis. Further, we identify a novel AKT phosphorylation site in BRCA1 at S694 which is responsive to activation of these signaling pathways. These data suggest AKT phosphorylation of BRCA1 increases total protein expression by preventing proteasomal degradation. AKT activation also appears to support nuclear localization of BRCA1, and co-expression of activated AKT with BRCA1 decreases radiation sensitivity, suggesting this interaction has functional consequences for BRCA1's role in DNA repair. Targets within this pathway could provide strategies for modulation of BRCA1 protein, which may prove therapeutically beneficial for breast and ovarian cancer treatment.
authors.affiliation: Department of Pathology, University of Colorado Denver, Aurora, CO 80045, USA.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Nelson
authors.forename: Traci R
authors.initials: TR
authors.lastname: Lyons
authors.forename: Christian D
authors.initials: CD
authors.lastname: Young
authors.forename: Kirk C
authors.initials: KC
authors.lastname: Hansen
authors.forename: Steven M
authors.initials: SM
authors.lastname: Anderson
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Holt
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology*; D004967:Estrogens / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D013058:Mass Spectrometry; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors
chemical_list: D019313:BRCA1 Protein; D018797:Cell Cycle Proteins; D004967:Estrogens; D011994:Recombinant Proteins; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D046988:Proteasome Endopeptidase Complex