title: Structural determinants of the BRCA1 : estrogen receptor interaction.
abstract: Previously, we showed that the BRCA1 protein interacts directly and functionally with estrogen receptor-alpha (ER-alpha), resulting in the inhibition of estradiol (E2)-stimulated ER-alpha transcriptional activity. The interaction sites were mapped to the N-terminus of BRCA1 (within amino acids (aa) 1-302) and the ligand-binding domain/activation function-2 (LBD/AF-2) region (within aa 282-420) of ER-alpha. In this study, we have further characterized the structure/function relationship for the BRCA1 : ER-alpha interaction. We found that the N-terminal RING domain (aa 20-64) is not required for the BRCA1 : ER-alpha interaction. We identified two separate contact points for ER-alpha, one within aa 1-100 and the other within aa 100-200 of BRCA1; and we showed that each of these BRCA1 peptides interacts with BRCA1 in vitro and in vivo. By using different fragments of the BRCA1 N-terminus, we found that aa 67-100 and 101-133 are required for the interaction with ER-alpha, but that aa 1-67 and 134-302 are dispensible. Previously, we showed that BRCA1 aa 1-302 does not inhibit E2-stimulated ER-alpha transcriptional activity but does bind to ER-alpha and acts as a dominant negative inhibitor of the full-length BRCA1 protein. Somewhat surprisingly, we found that BRCA1 aa 1-100 and BRCA1 aa 101-200 (but not aa 201-300) each inhibited ER-alpha activity, although not as efficiently as full-length BRCA1. Mutations within an HIV Rev-like nuclear export signal that resembles a nuclear receptor corepressor motif (aa 86-95) impaired the ability of both truncated (aa 1-100) and full-length (aa 1-1863) BRCA1 proteins to interact with and/or repress ER-alpha activity. Based on these findings, a partial BRCA1 : ER-alpha three-dimensional structure is proposed. The implications of these findings for understanding the BRCA1 : ER-alpha interaction are discussed.
authors.affiliation: Department of Oncology, Lombardi Cancer Center, Georgetown University, 3970 Reservoir Road, NW, Washington, DC 20057, USA.
authors.forename: Yong Xian
authors.initials: YX
authors.lastname: Ma
authors.forename: York
authors.initials: Y
authors.lastname: Tomita
authors.forename: Saijun
authors.initials: S
authors.lastname: Fan
authors.forename: Kongming
authors.initials: K
authors.lastname: Wu
authors.forename: Youzhi
authors.initials: Y
authors.lastname: Tong
authors.forename: Zeguo
authors.initials: Z
authors.lastname: Zhao
authors.forename: Liang-Nian
authors.initials: LN
authors.lastname: Song
authors.forename: Itzhak D
authors.initials: ID
authors.lastname: Goldberg
authors.forename: Eliot M
authors.initials: EM
authors.lastname: Rosen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019313:BRCA1 Protein / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D017124:Conserved Sequence; D019281:Dimerization; D047628:Estrogen Receptor alpha / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008958:Models, Molecular; D011471:Prostatic Neoplasms; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D019313:BRCA1 Protein; D047628:Estrogen Receptor alpha