BRCA1 function mediates a TRAP/DRIP complex through direct interaction with TRAP220.
Breast cancer susceptibility gene 1 (BRCA1) is a tumor suppressor gene mutated in a high percentage of hereditary breast and ovarian cancers. The multifunctional BRCA1 protein acts on cell cycle control, exerting several highly specialized DNA repair processes through diverse domains. Gene regulation through its C-terminal domain (BRCT) is indispensable for BRCA1-mediated tumor suppression, suggesting the possibility that the BRCT domain interacts with co-regulator complexes. Using a biochemical approach with HeLa S3 nuclear extracts, we isolated BRCT-associated complexes and identified one of the purified components as TRAP220. We then performed interaction studies in vivo (co-immunoprecipitation) and in vitro (glutathione S-transferase pull-down assays) and showed that BRCT directly interacted with TRAP220. This in vitro interaction was completely abolished by BRCT point mutations typical of those found in patients with BRCA1 that lack transactivation function. BRCA1 transactivation function was dependent on TRAP220 expression level in a transient expression assay. Moreover, a cell survival assay showed that antisense TRAP220 expression to disrupt endogenous TRAP220 expression significantly reduced the survival rate potentiated by BRCA1 after DNA damage. These results suggested that a TRAP220 complex play an important role as putative co-activator complexes in BRCA1-mediated tumor suppression.
Wada
Osamu
O
Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0034, Japan.
Oishi
Hajime
H
Takada
Ichiro
I
Yanagisawa
Junn
J
Yano
Tetsu
T
Kato
Shigeaki
S
D019313:BRCA1 Protein / Q000737:chemistry / Q000502:physiology*; D001943:Breast Neoplasms / Q000235:genetics; D004249:DNA Damage; D005260:Female; D006367:HeLa Cells; D006801:Humans; D056892:Mediator Complex; D056913:Mediator Complex Subunit 1; D009687:Nuclear Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D019313:BRCA1 Protein; C113182:DRIP, VDR interacting protein complex; C538855:MED1 protein, human; C491863:MED4 protein, human; D056892:Mediator Complex; D056913:Mediator Complex Subunit 1; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors