Insig2 3'UTR shortening by alternative polyadenylation escapes from miR-96-5p-mediated regulation and inhibits adipogenesis.

Abstract

Alternative polyadenylation (APA) is a key post-transcriptional regulatory mechanism in eukaryotes, but its role in adipogenesis remains poorly understood. Here, we investigated how insulin-induced gene 2 (Insig2) APA regulates adipogenesis. Functional assays showed that Insig2 knockdown promoted 3T3-L1 preadipocyte differentiation, whereas Insig2 overexpression inhibited it. During adipogenesis, Insig2 generated two APA isoforms with distinct 3'UTR lengths, and the short 3'UTR isoform was more abundant than the long isoform. Mechanistically, miR-96-5p specifically targeted the unique extension region of the long Insig2 3'UTR isoform to suppress its expression, thereby alleviating its inhibitory effect on adipogenesis. In contrast, the short Insig2 isoform lacked the miR-96-5p binding site and escaped miR-96-5p-mediated repression, thus exerting a stronger inhibitory effect on adipogenesis. Collectively, these findings reveal an isoform-specific Insig2 APA/miR-96-5p regulatory axis that dynamically controls adipogenesis at the post-transcriptional level. Our results revealed a new regulatory mechanism of Insig2 APA in adipogenesis.