In mammals, very long chain fatty acids (VLCFAs) perform pleiotropic roles in a wide range of biological processes, such as cell membrane formation, cell signal transduction, and endocrine regulation. Beef and milk are abundant of palmitic acid which can be further elongated into stearic acid for synthesizing VLCFAs. Elongase of very long chain fatty acid 6 (ELOVL6) is a rate-limiting enzyme for converting palmitic acid to stearic acid. Consequently, investigating the tissue expression patterns and transcriptional regulation of bovine ELOVL6 can provide new insights into improving the composition of beneficial fats in cattle and expanding the knowledge of transcriptional regulation mechanism among domestic animals. In the current study, we found that bovine ELOVL6 expressed ubiquitously. Dual-luciferase reporter assay identified that the core promoter region (-130/-41 bp) was located in the second CpG island. In addition, the deletion mutation of binding sites demonstrated that sterol regulatory element binding transcription factor 1 (SREBF1) and specific protein 1 (SP1) both were able to stimulate bovine ELOVL6 promoter activity independently, while resulting the similar effect. To confirm these findings, further RNA interference assays were executed in bovine mammary epithelial cells (BMECs). In summary, these data suggest that bovine ELOVL6 expressed ubiquitously and is activated by SREBF1 and SP1, via two binding sites present in the ELOVL6 promoter region between -130 bp to -41bp.
Fatty Acid Elongase 7 (ELOVL7) is the newly discovered protein on human that catalyzes the rate-limiting step towards the synthesis of very long-chain fatty acids and exhibits the highest activity toward C18: 3 (n-3) acyl-CoAs, which is the precursor of eicosapentaenoic acid (EPA, 20: 5n-3). However, in ruminants, an overall understanding of ELOVLs gene family and the transcriptional regulation of ELOVL7 remain unknown. The purpose of this study is to investigate the transcriptional regulation and the influence of bovine ELOVL7 in bovine mammary epithelial cells (bMECs). Quantitative real-time PCR analysis demonstrated that ELOVLs gene family had differential expression patterns in bMECs, and bovine ELOVL7 was expressed in a tissue-specific manner, which was high in kidney, followed by in abdominal fat and in bMECs. Promoter analysis of bovine ELOVL7, including bioinformatics analyzes, dual-luciferase reporter assays, protein pull-down assay, Western blot assay, over-expression and RNA interference assay, have independently and synthetically demonstrated that transcription factor Sp1 (SP1) specifically interacted with the GC-box at -143 to -128 base pair on ELOVL7 promoter. Furthermore, the exogenous α-linolenic acid (ALA, 18: 3n-3), strengthened the binding of SP1 to the ELOVL7 proximal promoter, resulting in the accumulation of lipid droplets in bMECs. In conclusion, these data suggest that the transcription of bovine ELOVL7 is affected by the binding of SP1 and the treatment of ALA, moreover, enlightening us the profound role of SP1 in modulating lipid synthesis of the mammary gland in cattle.
In order to produce a more efficient cancer cell death, a dual-functional polypeptide, xPolyR8-KLA(TPP), was synthesized by disulfide cross-linking CR8C and C-KLA(TPP). The obtained xPolyR8-KLA(TPP) could not only initiate tumor cell apoptosis by C-KLA(TPP) with improved cell penetrating ability, but was also capable of loading and delivering the tumor cell suppressing p53 gene. It was found that, after internalization by cancer cells, the xPolyR8-KLA(TPP)/p53 complex released the C-KLA(TPP) moiety and the p53 gene in the cytoplasm due to its reducible disulfide bonds. By regulating both the intrinsic and extrinsic apoptotic pathways, the xPolyR8-KLA(TPP)/p53 complex performed as a synergetic system and lead to a more efficient cancer cell death.
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