Poly(ADP-ribose) Polymerase-1 Down-regulates BRCA2 Expression through the BRCA2 Promoter

Abstract

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-kappaB, and Elf1) and a single factor that represses (SLUG) BRCA2 promoter activity have been reported. In addition, a 67-bp region (-582 to -516) associated with inhibition of promoter activity has been identified. However, it remains unclear how the 67-bp 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 67-bp 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 chromatin immunoprecipitation (ChIP) assays demonstrated that Parp-1 is associated with the BRCA2 promoter both in vitro and in vivo. Furthermore, Parp-1 inhibitors (either 3-AB or NU1025) and Parp-1 gene specific siRNA resulted in increased levels of endogenous BRCA2 expression. Inhibition of Parp-1 activity (by 3-AB) reduced histone 3 lysine 9 acetylation and blocked Parp-1 binding to the BRCA2 promoter. These results indicate that Parp-1 down-regulates BRCA2 expression through an interaction with a repression region of the BRCA2 promoter.