Detection of a novel transcription factor for the A alpha fibrinogen gene in response to interleukin-6.
The three fibrinogen genes belong to the class II hepatic acute phase proteins that are regulated in part by members of the interleukin-6 (IL-6) family of cytokines and glucocorticoids. The common DNA sequence that characterizes this group of proteins is a hexanucleotide CTGGGA residing in the promoter regions of these genes. Investigations of IL-6 control of the A alpha fibrinogen gene by electrophoretic mobility shift assays using a 30-base pair DNA probe containing the CTGGGA element revealed that a novel protein is associated with this site during non-IL-6-stimulated conditions. Sensitive time-course studies of IL-6 stimulation using primary hepatocyte cultures, high resolution polyacrylamide gel electrophoresis, and site-directed mutagenesis show that upon IL-6 stimulation of hepatocytes, this DNA binding protein transiently leaves the CTGGGA site and binds 12 base pairs down-stream but then begins to re-associate with the original DNA site at 1 h and is completed by 2 h. A recently characterized and cloned IL-6-activated transcription factor, Stat-3, which has been reported to bind a CT-GGGAA site in the alpha-2 macroglobulin gene, another member of the class II acute phase proteins, does not bind to the CTGGGA sequence in the A alpha fibrinogen gene. These findings reveal the presence of a previously undefined IL-6-regulated event, which involves a new DNA binding protein and demonstrates for the first time additional details of the kinetics of IL-6 control of fibrinogen gene expression.
Liu
Z
Z
Department of Cell Biology, University of Alabama at Birmingham 35294-0005, USA.
Fuller
G M
GM
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D015342:DNA Probes; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005340:Fibrinogen / Q000096:biosynthesis* / Q000235:genetics*; D007249:Inflammation; D007328:Insulin / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D014162:Transfection
D015342:DNA Probes; D004268:DNA-Binding Proteins; D007328:Insulin; D015850:Interleukin-6; D008070:Lipopolysaccharides; D014157:Transcription Factors; D005340:Fibrinogen