To better understand the link between chromatin modification and manganese superoxide dismutase (Mn-SOD) gene expression, we have investigated the level of histone acetylation at Mn-SOD proximal promoter. TSA induced the expression of Mn-SOD mRNA and its transcriptional activity in C2C12 cells. Sp1 binding sites in the proximal promoter region of Mn-SOD were transcriptionally responsive to TSA by transfection studies. We have detected a localized acetylation of histones H3 and H4, in vivo occupation by Sp1, early growth responsive-1 (Egr-1), and histone deacetylase-1 (HDAC1) in the proximal promoter region of Mn-SOD gene using chromatin immunoprecipitation assays. Our findings indicate that Mn-SOD gene expression is repressed by Sp1-HDAC1 complex. This repression is released by a localized histone acetylation and at least in parts a displacement by Egr-1 in response to TSA.