Role of NFBD1 in global gene expression

NFBD1 (nuclear factor with BRCT domains 1), also known as MDC1 (mediator of DNA damage signaling 1), is a protein involved in the ATM signaling pathway in response to DNA damage. In addition to a role in signaling, NFBD1 possesses transactivation activity, suggesting that it may influence transcription. Furthermore, NFBD1 affects p53-mediated transcription in the presence of the DNA damaging agent adriamycin. Our goal was to determine if NFBD1 affects global gene expression with or without ionizing radiation-induced DNA damage. Moreover, we sought to separate p53-dependent from p53-independent events. Illumina microarray analysis was carried out on RNA extracted from cells treated with and without NFBD1 shRNA and/or p53 shRNA in the presence and absence of DNA damage. Surprisingly, we found that the expression of NFBD1-regulated genes was changed in both the presence and absence of DNA damage. Furthermore, most NFBD1-regulated genes were regulated independently of p53. The identification of NFBD1-regulated genes was confirmed with a second NFBD1-directed shRNA sequence. The role of NFBD1 in global gene expression both in the presence and absence of ionizing radiation was determined. p53-dependent and p53-dependent events regulated by NFBD1 depletion were studied. U2OS cells were treated with control, NFBD1 shRNA, and/or p53 shRNA-expressing retrovirus. Cells were then treated with ionizing radiation and total RNA was isolated for Illumina microarray analysis.