miR-29b Targets LPL and TDG Genes and Regulates Apoptosis and Triglyceride Production in MECs.

microRNAs are involved in various biological processes by regulating the degradation or repressing the translation of target genes. In this study, the target genes of miR-29b were analyzed and predicted by bioinformatics. And lipoprotein lipase (LPL) and thymine DNA glycosylase (TDG) were selected for further validation by dual luciferase reporter assay. In addition, we investigated the effects of miR-29b on triglyceride synthesis and mammary epithelial cell (MEC) apoptosis. The result showed that luciferase activity was significantly lower in cells that miR-29b cotransfected with LPL and TDG gene reporter vectors (pmiR-RB-REPORT-LPL-WT, pmiR-RB-REPORT-TDG-WT) than in cells of miR-29b cotransfected with gene reporter vectors (pmiR-RB-REPORT-LPL-mut and pmiR-RB-REPORT-LPL-si; pmiR-RB-REPORT-TDG-mut and pmiR-RB-REPORT-TDG-si) (p < 0.05), indicating that target sites existed in 3'UTR of LPL and TDG. Furthermore, the expressions of miR-29b were negatively correlated with levels of mRNA and protein of LPL and TDG gene using quantitative real-time polymerase chain reaction and western blot analysis, suggesting that miR-29b might play an important role in regulation of LPL and TDG gene expression. Finally, miR-29b promoted triglyceride production and suppressed apoptosis in MECs, which might be attributed to the expressions of target genes LPL and TDG.