MCF10A cells in 3-D culture for 15 h after treatment with BRCA1-RNAi vs Luc-RNAi adenovirus

BRCA1 exerts transcriptional repression through interaction with CtIP in the C-terminal BRCT domain and ZBRK1 in the central domain. A dozen of genes including angiopoietin-1 (ANG1), a secreted angiogenic factor, are co-repressed by BRCA1 and CtIP based on microarray analysis of mammary epithelial cells in 3-D culture. BRCA1, CtIP and ZBRK1 form a complex that coordinately represses ANG1 expression via a ZBRK1 recognition site in ANG1 promoter. Impairment of this complex upregulates ANG1, which stabilizes endothelial cells forming capillary-like network structure. Consistently, Brca1-deficient mouse mammary tumors exhibit accelerated growth, pronounced vascularization and overexpressed ANG1. These results suggest, besides its role in maintaining genomic stability, BRCA1 directly regulates the expression of angiogenic factors to modulate the tumor microenvironment.

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Furuta S, Wang JM, Wei S, Jeng YM, Jiang X, Gu B, Chen PL, Lee EY, Lee WH