Journal
MARINE BIOTECHNOLOGY
Volume 21, Issue 4, Pages 475-487Publisher
SPRINGER
DOI: 10.1007/s10126-019-09895-w
Keywords
miR-33; insig1; srebp1; Delta 6 Delta 5fads2; elovl5; LC-PUFA biosynthesis
Funding
- National Key R&D Program of China [2018YFD0900400]
- National Natural Science Foundation of China [31873040, 31702357]
- Natural Science Foundation of Guangdong Province [2018A030313910]
- China Agriculture Research System [CARS-47]
- Guangdong Agriculture Research System (Freshwater Fish)
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Post-transcriptional regulatory mechanisms play important roles in the regulation of LC-PUFA biosynthesis. Our previous study revealed that miR-33 could increase the expression of fatty acyl desaturases (fads2) in the rabbitfish Siganus canaliculatus, but the specific mechanism is unknown. Here, we confirmed that miR-33 could target the 3 ' UTR of insulin-induced gene 1 (insig1), resulting in downregulation of its protein level in the rabbitfish hepatocyte line (SCHL). In vitro overexpression of miR-33 inhibited the mRNA level of insig1 and increased the mRNA levels of Delta 6 Delta 5 fads2 and elovl5, as well as srebp1. In SCHL cells, proteolytic activation of sterol-regulatory-element-binding protein-1 (Srebp1) was blocked by Insig1, with overexpression of insig1 decreasing mature Srebp1 level, while inhibition of insig1 led to the opposite effect. Srebp1 could enhance the promoter activity of Delta 6 Delta 5 fads2 and elovl5, whose expression levels decreased with knockdown of srebp1 in SCHL. Overexpression of miR-33 also resulted in a higher conversion of 18:3n-3 to 18:4n-3 and 20:5n-3 to 22:5n-3, linked to desaturation and elongation via Delta 6 Delta 5 Fads2 and Elovl5, respectively. The results suggested that the mechanism by which miR-33 regulates LC-PUFA biosynthesis in rabbitfish is through enhancing the expression of srebp1 by targeting insig1. The findings here provide more insight to the mechanism of miRNAs involvement in the regulation of LC-PUFA biosynthesis in teleosts.
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