Molecular Cloning, Characterization, and Expression Regulation of Acyl-CoA Synthetase 6 Gene and Promoter in Common Carp <i>Cyprinus carpio</i>

• Main Authors: Dizhi Xie, Zijie He, Yewei Dong, Zhiyuan Gong, Guoxing Nie, Yuanyou Li
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: International Journal of Molecular Sciences
• Subjects: acyl-CoA synthetase 6; transcriptional regulation; DHA deposition; <i>Cyprinus carpio</i>
• Online Access: https://www.mdpi.com/1422-0067/21/13/4736

Omega-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA), particularly docosahexaenoic acids (22:6n-3, DHA), have positive effects on multiple biologic and pathologic processes. Fish are the major dietary source of n-3 LC-PUFA for humans. Growing evidence supports acyl-coenzyme A (acyl-CoA) synthetase 6 (<i>acsl6</i>) being involved in cellular DHA uptake and lipogenesis in mammals, while its molecular function and regulatory mechanism remain unknown in fish. The present study focused on investigating the molecular characterization and transcription regulation of the <i>acsl6</i> gene in the freshwater teleost common carp (<i>Cyprinus carpio</i>). First, the full length of <i>acsl6</i> cDNA contained a coding region of 2148 bp for 715 amino acids, which possessed all characteristic features of the acyl-CoA synthetase (ACSL) family. Its mRNA expression was the highest in the brain, followed by in the heart, liver, kidney, muscle, and eyes, but little expression was detected in the ovary and gills. Additionally, a candidate <i>acsl6</i> promoter region of 2058 bp was cloned, and the sequence from −758 bp to −198 bp was determined as core a promoter by equal progressive deletion and electrophoretic mobility shift assay. The binding sites for important transcription factors (TFs), including stimulatory protein 1 (SP1), CCAAT enhancer-binding protein (C/EBPα), sterol-regulatory element binding protein 1c (SREBP1c), peroxisome proliferator activated receptor α (PPARα), and PPARγ were identified in the core promoter by site-directed mutation and functional assays. Furthermore, the intraperitoneal injection of PPARγ agonists (balaglitazone) increased the expression of <i>acsl6</i> mRNA, coupling with an increased proportion of DHA in the muscle, while opposite results were obtained in the injection of the SREBP1c antagonist (betulin). However, the expression of <i>acsl6</i> and DHA content in muscle were largely unchanged by PPARα agonist (fenofibrate) treatment. These results indicated that <i>acsl6</i> may play an important role for the muscular DHA uptake and deposition in common carp, and PPARγ and SREBP-1c are the potential TFs involved in the transcriptional regulation of <i>acsl6</i> gene. To our knowledge, this is the first report of the characterization of <i>acsl6</i> gene and its promoter in teleosts.