Human Breast Cancer Cell Line Mcf-7 In The Brca2 Promoter

Expression of the BRCA2 tumor suppressor gene is tightly linked to its roles in DNA damage repair and maintenance of chromosomal stability and genomic integrity. Three transcription factors that activate (USF, NF-κB and Elf1) and a single factor that represses (SLUG) BRCA2 promoter activity have been reported. In addition, a 67bp region (-582 to -516 upstream of transcription start site) associated with inhibition of promoter activity has been identified. However it remains unclear how the 67bp region contributes to regulation of BRCA2 expression. Here, we describe the affinity purification of a～120 kDa protein that binds to a silencer-binding region within the 67bp repression region of the BRCA2 promoter. Mass Spectrometry revealed the identity of the protein as poly-(ADP-ribose) polymerase-1 (Parp-1). Gel shift, antibody super-shift and ChIP assays demonstrated that Parp-1 is associated with the BRCA2 promoter both in vitro and in vivo. Furthermore, Parp-1 inhibitor (either 3-AB or NU1025) treatment and Parp-1 gene specific siRNA transfection resulted in increased levels of endogenous BRCA2 expression. Thus, Parp-1 down-regulates BRCA2 expression through an interaction with a repression region of the BRCA2 promoter.