PPAR beta in yellow catfish Pelteobagrus fulvidraco: molecular characterization, tissue expression and transcriptional regulation by dietary Cu and Zn

摘要

Peroxisome proliferator-activated receptor beta (PPAR beta) is a ligand-activated transcription factor that plays critical roles in the regulation of many important physiological processes. In this study, PPAR beta was cloned and characterized in yellow catfish Pelteobagrus fulvidraco. PPAR beta cDNA was 2350 bp in length with an open reading frame (ORF) of 1530 bp, encoding 509 amino acids, a 5'-untranslated region (UTR) of 474 bp, and a 3'-UTR of 346 bp. Similar to mammals, PPAR beta protein was predicted to consist of four domains, the A/B domain, DNA-binding domain (DBD), D domain, and ligand-binding domain (LBD). The DBD contained two zinc fingers with eight conserved cysteine residues. The predicted secondary structure of LBD consisted of 12 highly conserved alpha-helices and a small beta-sheet of 4 strands. In addition, PPAR beta was widely expressed across the tested tissues (liver, heart, muscle, intestine, brain, spleen, kidney, fat, ovary, and gill), but at the variable levels. Furthermore, the transcriptional responses of PPAR beta by dietary Cu and Zn levels were also investigated. Dietary Cu levels showed no significant effects on PPAR beta mRNA levels in the liver and intestine; in contrast, dietary Zn levels upregulated the hepatic PPAR beta mRNA levels, but not in the intestine. The present study serves to increase our understanding into the function of the PPAR beta gene in fish.