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Journal of dairy science

miR-26b promoter analysis reveals regulatory mechanisms by lipid-related transcription factors in goat mammary epithelial cells.


PMID 28527797

Abstract

MicroRNA (miRNA) regulate protein abundance and control diverse aspects of cellular processes and biological functions associated with lipid metabolism. MiR-26b and its host gene CTDSP1 regulate triacylglycerol synthesis by synergistically suppressing the insulin-induced gene 1 (INSIG1); however, the direct regulators of miR-26b expression remain unknown. In the present study, we characterized the activity of a novel putative promoter region in miR-26b. Results revealed that promoter activity and miR-26b expression are dynamically regulated by different transcription factors including peroxisome proliferator-activated receptor gamma (PPARG), sterol regulatory element binding transcription factor 1 (SREBF1), and liver X receptor α (LXRα). Two binding sites for the SREBF1 (SRE1 and SRE3) and the PPARG (peroxisome proliferator response element 1 and 2; PPRE1 and PPRE2), respectively, were identified in the miR-26b promoter, which demonstrated that those binding sites are responsible for the activation by PPARG and SREBF1. In silico analysis and site-directed mutagenesis of LXRα binding elements (LXRE) and SREBF1 binding elements (SRE) revealed that the effects of Ad-LXRα + T0901317 requires the presence of SRE, whereas potential LXRE had no effects on miR-26b expression. This suggested that regulation of miR-26b by LXRα is indirectly via an SRE, and miR-26b is regulated by transcription factors dually through DNA methylation and directly through binding to its promoter, all of which implies that regulation of miR-26b in ruminant mammary epithelial cells results from various mechanisms. In conclusion, we demonstrate a novel dual-regulatory mechanism whereby transcription factors regulate the expression of miR-26b. Overall, these findings contribute to our understanding of the interactions between specific promoter elements and the control of transcription and translation of miRNA.

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