Cytokine-inducible enhancer with promoter activity in both the rat and human manganese-superoxide dismutase genes

Diverse pro-inflammatory mediators regulate transcription of the gene (MnSO D) encoding the mitochondrial anti-oxidant protein manganese-superoxide dis mutase. Understanding the regulation of this gene is crucial to comprehendi ng its role in cytoprotection. In transfected lung epithelial cells, a huma n-growth-hormone reporter gene system was utilized to identify a potential enhancer in the MnSOD genomic fragment previously shown to contain multiple DNase-I-hypersensitive sites. Northern analysis demonstrated a 10-20-fold increase in response to pro-inflammatory mediators, Inclusion of the MnSOD genomic fragment in reporter constructs was necessary to mimic these stimul us-dependent endogenous levels. The inducible enhancer element was localize d to a 260 bp fragment in intron 2, coinciding with a previously defined DN ase-I-hypersensitive site. This element functions in an orientation- and po sition-independent manner as well as with the heterologous thymidine kinase promoter. In addition, we have demonstrated that a homologous sequence wit hin the human MnSOD gene exhibits identical enhancer activity. A novel char acteristic of the rat and human enhancer elements involves the ability to p romote cytokine-inducible transcription in the absence of a classical promo ter.