Transcriptional regulation of insulin receptor gene promoter in rat hepatocytes.
To investigate the DNA regulatory sequences -618 to -593 (initiator ATG is +1) of the insulin receptor (IR) promoter required for IR gene expression, primary cultured hepatocytes of rats were transfected with plasmids containing the 5'-flanking sequences of the rat IR gene fused to the luciferase gene. When three copies of the nucleotides -618 to -593 of the IR promoter were transfected, the reporter activity was significantly increased in the presence of glucose and more increased in the presence of glucose/insulin. The glucose/insulin stimulation was inhibited by the addition of polyunsaturated fatty acids. These results were similar to those found earlier for the transcriptions of the fatty acid synthase, FAS(-57/-35), ATP citrate-lyase, ACL(-64/-41), and leptin(-101/-83) genes, which promoter sequences have a high similarity to IR(-618/-593). However, similarly to the leptin gene, the IR gene was more responsive to glucose stimulation than the FAS and ACL genes. Mutation of either one of the Sp1 binding sites (-618/-593) did not significantly affect the transcription, whereas mutation of three or four Sp1 binding sites resulted in a loss of responsiveness to glucose/insulin. Gel mobility shift assays revealed that nuclear factor(s) from rat liver specifically formed complexes with the sequence of IR(-618/-593). By antibody supershift assays, the transcription factors Sp1and Sp3 were found to bind with the IR(-618/-593). The IR, leptin, ACL and FAS genes contain common DNA-sequences responsible for the glucose/insulin-stimulation, suggesting that these genes are similarly regulated.
Fukuda
H
H
Faculty of Human and Cultural Studies, Tezukayama Gakuin University, Sakai, Osaka, 590-0113, Japan.
Noguchi
T
T
Iritani
N
N
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D020738:Leptin / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008297:Male; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D051705:Sp3 Transcription Factor; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D005231:Fatty Acids, Unsaturated; D007328:Insulin; D020738:Leptin; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; C497123:Sp3 protein, rat; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D004247:DNA; D008156:Luciferases; D011972:Receptor, Insulin; D005947:Glucose