Multiple Roles for Steroid Receptor RNA Activator (SRA) in Regulation of Adipogenesis and Insulin Sensitivity. Mus musculus

PPARγ is a master transcriptional regulator of adipogenesis. Hence, the identification of PPARγ coactivators should help reveal mechanisms controlling gene expression in adipose tissue development and physiology. We show that the non-coding RNA Steroid receptor RNA Activator, SRA, associates with PPARγ and coactivates PPARγ-dependent reporter gene expression. Overexpression of SRA in ST2 adipocyte precursor cells promotes their differentiation into adipocytes. Conversely, knockdown of endogenous SRA inhibits 3T3-L1 preadipocyte differentiation. Microarray analysis reveals hundreds of SRA-responsive genes in adipocytes, including genes in cell cycle, insulin and TNFα signaling pathways. Some functions of SRA may involve mechanisms other than coactivation of PPARγ. SRA increases insulin-stimulated glucose uptake in adipocytes. SRA promotes S-phase entry during mitotic clonal expansion, decreases expression of cyclin-dependent kinase inhibiters p21Cip1 and p27Kip1, and increases phosphorylation of Cdk1/Cdc2. SRA also inhibits the TNFα-induced phosphorylation of c-Jun NH2-terminal kinase. In conclusion, SRA enhances adipogenesis and adipocyte function through multiple pathways. Overall design: Total RNA was isolated from fully differentiated (MDIT day 4) SRA overexpressing (pMSCV-SRA) and control (pMSCV empty vector) ST2 adipocytes, or fully differentiated (MDIT day 8) shSRA knockdown (pSuperior-shSRA) or shControl (pSuperior-shcontrol) 3T3-L1 adipocytes. Genome wide gene expression analysis was performed using Affymetrix mouse genome 430 2.0 arrays. Triplicate samples were analyzed.