Regulation of the rat SREBP-1c promoter in primary rat hepatocytes.
We have cloned 5 kb of genomic DNA encompassing 1.72 kb of 5'-regulatory sequence and exons 1-c and 2 of the rat SREBP-1c gene. A 1.5-kb segment upstream from the transcription start site was ligated ahead of the luciferase reporter gene and tested for promoter activity by transient transfection assays in primary rat hepatocytes. We discovered that insulin strongly activated the full-length promoter, regardless of whether 5 or 20 mM glucose was in the culture medium during treatment. Stimulation by insulin was blocked by dibutyryl-cAMP and by polyunsaturated fatty acids, such as alpha-linolenic acid, gamma-linolenic acid, or eicosapentaenoic acid; palmitic or oleic acids, however, had no inhibitory effect. A truncated promoter containing 149 bp of 5' flanking DNA, including proximal NF-Y, E-box, SRE, and Sp1 sites, retained most of the response. This is the first report that insulin, cAMP, and polyunsaturated fatty acids modulate the proximal SREBP-1c promoter in rat hepatocytes mirroring physiological regulation of SREBP-1c in vivo.
Deng
Xiong
X
Department of Veterans Affairs Medical Center, Memphis, Tennessee, USA.
Cagen
Lauren M
LM
Wilcox
Henry G
HG
Park
Edwards A
EA
Raghow
Rajendra
R
Elam
Marshall B
MB
D000818:Animals; D001483:Base Sequence; D003994:Bucladesine / Q000378:metabolism; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics*; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005091:Exons; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005947:Glucose / Q000494:pharmacology; D022781:Hepatocytes / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D019301:Oleic Acid / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051780:Sterol Regulatory Element Binding Protein 1; D013997:Time Factors; D014157:Transcription Factors; D014158:Transcription, Genetic; D014162:Transfection; D017965:gamma-Linolenic Acid / Q000378:metabolism
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007328:Insulin; D012333:RNA, Messenger; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D019301:Oleic Acid; D019308:Palmitic Acid; D012313:RNA; D003994:Bucladesine; D017965:gamma-Linolenic Acid; D015118:Eicosapentaenoic Acid; D000242:Cyclic AMP; D008156:Luciferases; D005947:Glucose