UHRF1 is associated with epigenetic silencing of BRCA1 in sporadic breast cancer.

BRCA1 is closely related to the pathogenesis of breast cancer, BRCA1 mRNA is reduced in sporadic breast cancer cells despite the lack of mutations. In the present report, we found that overexpression of UHRF1 (ubiquitin-like, containing PHD and RING finger domains 1) was closely related to DNA methylation, deacetylation, and methylation of histones, recruitment of an inhibiting transcriptional complex on the BRCA1 promoter in sporadic breast cancer. Overexpression of UHRF1 induced deacetylation of histones H3 and H4, which was facilitated by recruitment of histone deacetylase1 (HDAC1) to the BRCA1 promoter. Loss of acetylation was accompanied by loss of binding of the key transcription factors MyoD, CBP, and p300. UHRF1 also recruited histone lysine methyltransferase G9a to the BRCA1 promoter and histone 3 lysine 4 (H3K4) was demethylated, and histone 3 lysine 9 (H3K9) was methylated. Finally, overexpression of UHRF1 leaded to methylation of BRCA1 promoter by recruitment of DNMT1 to the BRCA1 promoter, locking in marked suppression of BRCA1. It is the first to describe that UHRF1 is responsible for regulating BRCA1 transcription by inducing DNA methylation, histone modifications, and recruitment of transcriptional complex on the BRCA1 promoter, UHRF1 is a new bio-marker in sporadic breast cancer.