Three NF-kappa B sites in the I kappa B-alpha promoter are required for induction of gene expression by TNF alpha.
NF-kappa B was first identified as a postive regulator which bound to a 10 bp sequence in the first intron of the Ig kappa light chain gene. Further characterization of this transcription factor has revealed that NF-kappa B is kept from binding to its consensus sequence by its inhibitor, IkB-alpha, which retains NF-kappa B in the cytoplasm. Upon receiving various extra- and intracellular signals, I kappa B-alpha is rapidly degraded and NF-kappa B is induced to translocate into the nucleus. This process precedes the rapid induction of I kappa B-alpha mRNA and protein. To understand how I kappa B-alpha is replenished, we have cloned and sequenced the 5' flanking region of the I kappa B-alpha gene and have identified the transcription start site and three NF-kappa B sites in this region. Further characterization of these NF-kappa B sites show that they have different affinities for three specific protein complexes which we identify here to consist of various members of the Rel family. In transient assays, cotransfection with a p65 expression vector is able to activate an I kappa B-alpha promoter-CAT reporter construct and all three NF-kappa B sites are required for full activation of the I kappa B-alpha gene following stimulation with TNF-alpha. Our data confirm a transcriptional autoregulatory loop involved in maintaining appropriate NF-kappa B and I kappa B-alpha levels in the cell.
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Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill 27599.
Kazantsev
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Baldwin
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D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D004247:DNA