Increased hepatic UCP2 expression in rats with nonalcoholic steatohepatitis is associated with upregulation of Sp1 binding to its motif within the proximal promoter region.
Uncoupling protein-2 (UCP2) is a mitochondrial inner-membrane carrier protein that is involved in the control of fatty acid metabolism. To understand the mechanism of the transcriptional regulation of ucp2 in the pathogenesis of nonalcoholic steatohepatitis (NASH), we cloned 500 bp upstream of the ucp2 exon 1 from a rat liver cDNA library and identified cis-acting regulatory elements. The transcriptional start site was identified as "C," -359 bp from the ATG codon. A reporter gene assay showed that deletion of the nucleotide sequence between -264 and -60 bp resulted in a significant decrease in promoter activity in HepG2 and H4IIE cells. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) revealed that the increase in promoter activity is related to an enhanced ability of Sp1 to bind to its motifs at -84 to -61 bp within the ucp2 proximal promoter. Overexpression of exogenous Sp1 in H4IIE cells also increased the promoter activity. We demonstrated that the expression of UCP2 mRNA and protein is markedly increased in rats with nonalcoholic steatohepatitis (NASH). Coincidently, levels of Sp1 binding to -84/-61 bp were also increased. Overall, our data indicate that the Sp1-binding site located at the proximal promoter is involved in the regulation of rat UCP2 expression.
Jiang
Ying
Y
Department of Cell Biology and Municipal Laboratory for Liver Protection and Regulation of Regeneration, Capital Medical University, 100069 Beijing, China.
Zhang
Hua
H
Dong
Ling-Yue
LY
Wang
Dan
D
An
Wei
W
D000438:Alcohols; D000818:Animals; D045744:Cell Line, Tumor; D006505:Hepatitis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D008111:Liver Function Tests; D008297:Male; D008854:Microscopy, Electron; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D016329:Sp1 Transcription Factor / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics; D000071246:Uncoupling Protein 2; D015854:Up-Regulation
D000438:Alcohols; D007473:Ion Channels; D024101:Mitochondrial Proteins; D016329:Sp1 Transcription Factor; C000604391:Ucp2 protein, rat; D000071246:Uncoupling Protein 2