School of Marine Sciences, South China Agricultural University, Guangzhou 510642, China.
Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China.
Int J Mol Sci. 2018 Oct 16;19(10):3193. doi: 10.3390/ijms19103193.
The rabbitfish is the first marine teleost shown to be able to biosynthesize long-chain polyunsaturated fatty acids (LC-PUFA) from C18 PUFA precursors catalyzed by two fatty acyl desaturases (fad) including Δ4 Fad and Δ6/Δ5 Fad as well as two elongases (Elovl4 and Elovl5). Previously, hepatocyte nuclear factor 4α (Hnf4α) was demonstrated to be predominant in the transcriptional regulation of two . To clarify the regulatory mechanisms involved in rabbitfish lipogenesis, the present study focused on the regulatory role of Hnf4α to expression and LC-PUFA biosynthesis. Bioinformatics analysis predicted two potential Hnf4α elements in promoter, one binding site was confirmed to interact with Hnf4α by gel shift assays. Moreover, overexpression of caused a remarkable increase both in elovl5 promoter activity and mRNA contents, while knock-down of hnf4α in hepatocyte line (SCHL) resulted in a significant decrease of gene expression. Meanwhile, overexpression enhanced LC-PUFA biosynthesis in SCHL cell, and intraperitoneal injection to rabbitfish juveniles with Hnf4α agonists (Alverine and Benfluorex) increased the expression of , and Δ4 , coupled with an increased proportion of total LC-PUFA in liver. The results demonstrated that Hnf4α is involved in LC-PUFA biosynthesis by up-regulating the transcription of the gene in rabbitfish, which is the first report of Hnf4α as a transcription factor of the gene in vertebrates.
兔鱼是第一个被证明能够通过两种脂肪酰去饱和酶（fad），包括 Δ4 Fad 和 Δ6/Δ5 Fad 以及两种延伸酶（Elovl4 和 Elovl5），将 C18 PUFA 前体生物合成长链多不饱和脂肪酸（LC-PUFA）的海洋硬骨鱼。此前，已证明肝细胞核因子 4α（Hnf4α）在两种基因的转录调控中占主导地位。为了阐明兔鱼脂肪生成中涉及的调控机制，本研究重点研究了 Hnf4α 对基因表达和 LC-PUFA 生物合成的调控作用。生物信息学分析预测了基因启动子中两个潜在的 Hnf4α 元件，通过凝胶迁移分析证实了一个结合位点与 Hnf4α 相互作用。此外，过表达基因导致 Elovl5 启动子活性和 mRNA 含量显著增加，而 SCHL 肝细胞系中 hnf4α 的敲低导致基因表达显著下降。同时，基因过表达增强了 SCHL 细胞中的 LC-PUFA 生物合成，腹腔注射 Hnf4α 激动剂（Alverine 和 Benfluorex）可增加兔鱼幼鱼肝脏中基因的表达、和 Δ4 的表达，以及总 LC-PUFA 的比例增加。这些结果表明，Hnf4α 通过上调兔鱼基因的转录来参与 LC-PUFA 的生物合成，这是 Hnf4α 作为脊椎动物基因转录因子的首次报道。
