Transcriptional regulation of the 5' proximal promoter of the human manganese superoxide dismutase gene.
Manganese superoxide dismutase (MnSOD) is a primary antioxidant enzyme critical for maintaining normal cell function and for survival. Previously, we cloned the entire MnSOD gene, including a 0.782-kb 5' DNA sequence, from a human embryonic lung fibroblast cell line. Sequence analysis indicates that the promoter of the human MnSOD gene is TATA-less and CAAT-less, and the DNA sequence immediately upstream from the transcription start site is GC rich. To study the function and regulation of the human MnSOD promoter, we cloned a 257-bp sequence (P7) containing the transcription start site and the 5' GC-rich region. Consensus analysis and DNase I footprinting assay indicated that P7 contains multiple Sp1- and AP-2-binding sites. Deletions of the P7 sequence diminished the promoter activity and decreased the response to Sp1 protein. The first three Sp1 consensus sites were required for high promoter activity in mammalian cells and enhanced promoter activity in Drosophila Schneider Line 2 (SL2) cells. In the SL2 cells, Sp1 activated the P7 activity in a dose-dependent manner. In contrast, cotransfections with AP-2 expression vector marginally increased P7 activities in human hepatocarcinoma HepG2 cells. The results suggest that Sp1 is an important regulator for the transcriptional activities of P7, whereas AP-2 is a minor activator for P7 and competes with Sp1 for binding sites which may downregulate P7 function.
Yeh
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Graduate Center for Toxicology, University of Kentucky, Lexington 40536, USA.
Wan
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St Clair
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D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002461:Cell Line, Transformed; D003001:Cloning, Molecular; D004247:DNA; D004268:DNA-Binding Proteins / Q000502:physiology; D004330:Drosophila; D029721:Drosophila Proteins; D015971:Gene Expression Regulation, Enzymologic; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000502:physiology; D013482:Superoxide Dismutase / Q000235:genetics*; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D016329:Sp1 Transcription Factor; C493674:TfAP-2 protein, Drosophila; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D004247:DNA; D013482:Superoxide Dismutase