The human topoisomerase I gene promoter is regulated by NF-IL6.
We investigated the expression of the human DNA topoisomerase I (hTOP1) gene in HeLa cells and in adenovirus-transformed 293 cells. A highly conserved proximal promoter element is essential for hTOP1 promoter activity in HeLa cells but not in 293 cells. This correlates with the presence of specific promoter-binding proteins in HeLa cells and their absence in 293 cells. We identified the HeLa binding protein by screening a cDNA expression library with the specific promoter site as a probe and demonstrate now that the activating protein is identical to the nuclear factor for interleukin-6 expression (NF-IL6), a member of the C/EBP family of transcription factors. Overexpression of NF-IL6 strongly stimulates hTOP1 promoter activity in HeLa cells, suggesting that NF-IL6 is a major hTOP1-regulating protein. Because of the presence of adenovirus protein E1A, 293 cells express the hTOP1 gene more efficiently than HeLa cells but do not contain NF-IL6 activity. E1A activation of the hTOP1 promoter is suppressed by NF-IL6 overexpression. This result supports previous observations concerning a functional interaction between viral protein E1A and NF-IL6. Finally, we show that hTOP1 gene expression in differentiating macrophages is correlated with the synthesis of NF-IL6-specific mRNA.
Division of Biology, Universität Konstanz, Germany.
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Heiland
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Knippers
D000260:Adenoviruses, Human / Q000235:genetics; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins; D002461:Cell Line, Transformed; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000378:metabolism; D017124:Conserved Sequence; D004264:DNA Topoisomerases, Type I / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000378:metabolism*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D015500:Chloramphenicol O-Acetyltransferase; D004264:DNA Topoisomerases, Type I