Functional Analysis of Promoters of Genes in Lipid Metabolism and Their Transcriptional Response to STAT3 under Leptin Signals

We characterized the promoters of target genes of the signal transducer and activator of transcription 3, STAT3 (carnitine palmitoyltransferase I, CPT I alpha 1b, acetyl-CoA carboxylase alpha, ACC alpha; fatty acid synthase, FAS; and peroxisome proliferator-activated receptor gamma, PPAR gamma) in a teleost Pelteobagrus fulvidraco. Binding sites of STAT3 were predicted on these promoters, indicating that STAT3 probably mediated their transcriptional activities. Leptin had no effect on the activity of ACC a and PPAR g promoters, but increased CPT I alpha 1b promoter activity and decreased FAS promoter activity. The 979/997 STAT3 binding site of CPT I alpha 1b and the 794/812 STAT3 binding site of FAS were functional binding loci responsible for leptin-induced transcriptional activation. The study provided direct evidence that STAT3 regulated the expression of CPT I alpha 1b and FAS at the transcription level, and determined the STAT3 response element on promoters of CPT I alpha 1b and FAS under leptin signal.