Long Noncoding RNA Meg3 Regulates Mafa Expression in Mouse Beta Cells by Inactivating Rad21, Smc3 or Sin3α.

<bold><italic>Background/Aims:</italic></bold><bold><italic></italic></bold> The main pathogenic mechanism of diabetes is a decrease in the number of islet beta cells or a decline in their function. Recent studies have shown that pancreatic long noncoding RNAs (lncRNAs) have a high degree of tissue specificity and may be involved in the maintenance of islet cells function and the development of diabetes. The aim of this study was to investigate the molecular regulatory mechanism of mouse maternal expressed gene 3 (Meg3) in insulin biosynthesis in pancreatic islets. <bold><italic>Methods:</italic></bold><bold><italic></italic></bold> Chromatin immunoprecipitation–quantitative polymerase chain reaction (qPCR) and RNA immunoprecipitation–qPCR were used to investigate the molecular mechanism of lncRNA Meg3 in insulin biosynthesis by regulating v-Maf musculoaponeurotic fibrosarcoma oncogene family, protein A (MafA), a mature beta cell marker in the MIN6 beta cell line. Further, the expression levels of <italic>Meg3, Ezh2, MafA, Rad21, Smc3</italic>, and <italic>Sin3α</italic> were analyzed <italic>in vivo</italic> and <italic>in vitro</italic> by RT-PCR and western blotting. <bold><italic>Results:</italic></bold><bold><italic></italic></bold> Intranuclear lncRNA Meg3 can bind EZH2, a methyltransferase belonging to the Polycomb repressive complex-2, in pancreatic islet cells. In addition, knockdown of <italic>Ezh2</italic> can also inhibit the expression of <italic>MafA</italic> and <italic>Ins2</italic>, while expression levels of <italic>Rad21, Smc3</italic>, and <italic>Sin3α</italic> are upregulated, by interfering with <italic>Ezh2</italic> or <italic>Meg3</italic> in pancreatic beta cells. Knockdown of <italic>Meg3</italic> resulted in the loss of EZH2 binding and H3K27 trimethylation occupancy of <italic>Rad21, Smc3</italic>, and <italic>Sin3α</italic> promoter regions. The inhibition of <italic>Rad21, Smc3</italic>, or <italic>Sin3α</italic>, which directly act on the <italic>MafA</italic> promoter, leads to upregulated expression of <italic>MafA</italic> in both MIN6 cells and mouse islets. Moreover, the synthesis and secretion of insulin were increased by inhibition of these transcription factors. <bold><italic>Conclusions:</italic></bold><bold><italic></italic></bold> Pancreatic lncRNA Meg3 can epigenetically regulate the expression of <italic>Rad21, Smc3</italic>, and <italic>Sin3α</italic> via EZH2-driven H3K27 methylation. By inhibiting the expression of <italic>Rad21, Smc3</italic>, or <italic>Sin3α</italic>, Meg3 promotes the expression of <italic>MafA</italic> and affects the production of insulin. [ABSTRACT FROM AUTHOR]