Dataset Information

Hnf4? Is Involved in LC-PUFA Biosynthesis by Up-Regulating Gene Transcription of Elongase in Marine Teleost Siganus canaliculatus.

ABSTRACT: The rabbitfish Siganus canaliculatus 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 ?4 Fad and ?6/?5 Fad as well as two elongases (Elovl4 and Elovl5). Previously, hepatocyte nuclear factor 4? (Hnf4?) was demonstrated to be predominant in the transcriptional regulation of two fads. To clarify the regulatory mechanisms involved in rabbitfish lipogenesis, the present study focused on the regulatory role of Hnf4? to elovl5 expression and LC-PUFA biosynthesis. Bioinformatics analysis predicted two potential Hnf4? elements in elovl5 promoter, one binding site was confirmed to interact with Hnf4? by gel shift assays. Moreover, overexpression of hnf4? caused a remarkable increase both in elovl5 promoter activity and mRNA contents, while knock-down of hnf4? in S. canaliculatus hepatocyte line (SCHL) resulted in a significant decrease of elovl5 gene expression. Meanwhile, hnf4? overexpression enhanced LC-PUFA biosynthesis in SCHL cell, and intraperitoneal injection to rabbitfish juveniles with Hnf4? agonists (Alverine and Benfluorex) increased the expression of hnf4?, elvol5 and ?4 fad, coupled with an increased proportion of total LC-PUFA in liver. The results demonstrated that Hnf4? is involved in LC-PUFA biosynthesis by up-regulating the transcription of the elovl5 gene in rabbitfish, which is the first report of Hnf4? as a transcription factor of the elovl5 gene in vertebrates.

SUBMITTER: Li Y

PROVIDER: S-EPMC6214118 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Hnf4α Is Involved in LC-PUFA Biosynthesis by Up-Regulating Gene Transcription of Elongase in Marine Teleost Siganus canaliculatus.

Li Yuanyou Y Zeng Xiaowei X Dong Yewei Y Chen Cuiying C You Cuihong C Tang Guoxia G Chen Junliang J Wang Shuqi S

International journal of molecular sciences 20181016 10

The rabbitfish Siganus canaliculatus 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 fads. To clarify the regulatory mechanisms involved in rabbitfish ...[more]

PMID: 30332813

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Project description:The rabbitfish Siganus canaliculatus was the first marine teleost demonstrated to have the ability for the biosynthesis of long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA) from C18 PUFA precursors, and all the catalytic enzymes including two fatty acyl desaturase 2 (Δ4 Fads2 and Δ6/Δ5 Fads2) and two elongases (Elovl4 and Elovl5) have been identified, providing a good model for studying the regulatory mechanisms of LC-PUFA biosynthesis in fish. Stimulatory protein 1 (Sp1) has been speculated to be a vital transcription factor in determining the promoter activity of Fads-like genes in fish, however its regulatory effects on gene expression and LC-PUFA biosynthesis have not been demonstrated. Bioinformatic analysis predicted potential Sp1 binding sites in the promoters of the rabbitfish Δ6/Δ5 fads2 and elovl5, but not in Δ4 fads2 promoter. Here we cloned full-length cDNA of the rabbitfish sp1 gene, which encoded a putative protein of 701 amino acids, and was expressed in all tissues studied with highest levels in gill and eyes. The dual luciferase reporter assay in HepG2 line cells demonstrated the importance of the Sp1 binding site for the promoter activities of both Δ6/Δ5 fads2 and elovl5. Moreover, the electrophoretic mobility shift assay confirmed the direct interaction of Sp1 with the two promoters. Insertion of the Sp1 binding site of Δ6/Δ5 fads2 promoter into the corresponding region of the Δ4 fads2 promoter significantly increased activity of the latter. In the Siganus canaliculatus hepatocyte line (SCHL) cells, mRNA levels of Δ6/Δ5 fads2 and elovl5 were positively correlated with the expression of sp1 when sp1 was overexpressed or knocked-down by RNAi or antagonist (mithramycin) treatment. Moreover, overexpression of sp1 also led to a higher conversion of 18:2n-6 to 18:3n-6, 18:2n-6 to 20:2n-6, and 18:3n-3 to 20:3n-3, which related to the functions of Δ6/Δ5 Fads2 and Elovl5, respectively. These results indicated that Sp1 is involved in the transcriptional regulation of LC-PUFA biosynthesis by directly targeting Δ6/Δ5 fads2 and elovl5 in rabbitfish, which is the first report of Sp1 involvement in the regulation of LC-PUFA biosynthesis in vertebrates.

Dataset Information

Hnf4? Is Involved in LC-PUFA Biosynthesis by Up-Regulating Gene Transcription of Elongase in Marine Teleost Siganus canaliculatus.

Publications

Hnf4α Is Involved in LC-PUFA Biosynthesis by Up-Regulating Gene Transcription of Elongase in Marine Teleost <i>Siganus canaliculatus</i>.

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