The transcriptional factor PPARab positively regulates elovl5 elongase in golden pompano trachinotus ovatus (Linnaeus 1758)

Abstract

The nuclear peroxisome proliferator-activated receptors (PPARs) regulate the transcription of elongases of very long-chain fatty acids (Elovl), which are involved in polyunsaturated fatty acid (PUFA) biosynthesis in mammals. In the present study, we first characterized the function of Elovl5 elongase in Trachinotus ovatus. The functional study showed that ToElovl5 displayed high elongation activity toward C18 and C20 PUFA. To investigate whether PPARab was a regulator of Elovl5, we also reported the sequence of T. ovatus PPARab (ToPPARab). The open reading frame (ORF) sequence encoded 469 amino acids possessing four typical characteristic domains, including an N-terminal hypervariable region, a DNA-binding domain (DBD), a flexible hinge domain and a ligand-binding domain (LBD). Thirdly, promoter activity experiments showed that the region from PGL3-basic-Elovl5-5 (-146 bp to +459 bp) was defined as the core promoter by progressive deletion mutation of Elovl5. Moreover, PPARab overexpression led to a clear time-dependent enhancement of ToElovl5 promoter expression in HEK 293T cells. Fourth, the agonist of PPARab prominently increased PPARab and Elovl5 expression, while PPARab depletion by RNAi or an inhibitor was correlated with a significant reduction of Elovl5 transcription in T. ovatus caudal fin cells (TOCF). In conclusion, the present study provides the first evidence of the positive regulation of Elovl5 transcription by PPARab and contributes to a better understanding of the transcriptional mechanism of PPARab in fish.