The regulation of catalase gene expression in mouse muscle cells is dependent on the CCAAT-binding factor NF-Y

Catalase is an antioxidant enzyme whose expression is transcriptionally regulated and tissue-specific. The level of expression determines, in part, the susceptibility of a cell to oxidative stress. Skeletal muscle is a tissue that experiences high levels of oxidative stress during normal metabolic activity, so the expression of antioxidant enzymes is critical to preventing cellular damage. To study the transcriptional regulation of the catalase gene in mouse muscle cells, the 5'-flanking region of the mouse catalase gene was isolated from genomic DNA. The transcriptional activity of the 5'-flanking region was investigated in transiently transfected murine myoblasts using a promoter-less luciferase reporter vector and site-directed mutagenesis. Strikingly, we found that nearly all of the transcriptional activity was restricted to the final 191 bp of the greater than 2.5 kb of the 5'-flanking region examined. Of the potential consensus binding sites for transcriptional regulators within this 191-bp region, we identified two CCAAT boxes and no other consensus sites that were important for the transcriptional activity of this promoter. Gel shift and super shift assays indicated that the transcription factor NF-Y bound to both CCAAT boxes. Furthermore, co-transfection of reporter constructs with NF-Y expression vectors into Drosophila SL2 cells demonstrated NF-Y-mediated transcriptional activation of the catalase gene. Interestingly, there were no nearby sites that appeared to interact with either NF-Y binding sites, and thus it appears that NF-Y acts as a bona fide transcription factor for catalase gene expression in mouse muscle cells. These data provide the first examination of the regulation of the mouse catalase gene and indicate unique aspects of its regulation that may pertain to the tissue-specific patterns of expression.