Sp1-mediated transcriptional regulation of NFBD1/MDC1 plays a critical role in DNA damage response pathway

• Published in: Genes to cells : devoted to molecular & cellular mechanisms 2008-01, Vol.13 (1), p.53-66
• Main Authors: Bu, Youquan, Suenaga, Yusuke, Ono, Sayaka, Koda, Tadayuki, Song, Fangzhou, Nakagawara, Akira, Ozaki, Toshinori
• Format: Article
• Language: English
• Subjects: Base Sequence; Cell Line, Tumor; DNA Damage; DNA-Binding Proteins - genetics; DNA-Binding Proteins - physiology; Gene Expression Regulation; Humans; Molecular Sequence Data; Nuclear Proteins - genetics; Nuclear Proteins - physiology; Plicamycin - analogs & derivatives; Plicamycin - pharmacology; Promoter Regions, Genetic; Signal Transduction; Sp1 Transcription Factor - antagonists & inhibitors; Sp1 Transcription Factor - genetics; Sp1 Transcription Factor - physiology; Trans-Activators - genetics; Trans-Activators - physiology
• ISSN: 1356-9597; 1365-2443
• DOI: 10.1111/j.1365-2443.2007.01144.x

NFBD1/MDC1 is a large nuclear protein with an anti-apoptotic potential which participates in DNA damage response. Recently, we have demonstrated that NFBD1 has an inhibitory effect on pro-apoptotic p53 and DNA damage-induced transcriptional repression of NFBD1 plays an important role in p53-dependent apoptotic response. In this study, we have found that NFBD1 promoter region contains canonical Sp1-, STAT-1- and NF-Y-binding sites and finally we have identified Sp1 as a transcriptional activator for NFBD1. The 5'-RACE and bioinformatic analyses revealed that NFBD1 encodes at least four transcriptional variants arising from distinct transcriptional start sites. Luciferase reporter assays using a series of NFBD1 promoter deletion mutants demonstrated that the proximal Sp1-binding site is required for the transcriptional activation of NFBD1. Indeed, the endogenous Sp1 was recruited onto the proximal Sp1-binding site as examined by chromatin immunoprecipitation (ChIP) assay and siRNA-mediated knockdown of the endogenous Sp1 in HeLa cells reduced the expression levels of NFBD1, which renders cells sensitive to adriamycin (ADR). In support of this notion, mithramycin A (MA, Sp1 inhibitor) treatment resulted in a significant down-regulation of NFBD1. Taken together, our present findings suggest that Sp1-mediated transcriptional regulation of NFBD1 plays an important role in the regulation of DNA damage response.