Mouse Elovl-6 promoter is an SREBP target

Elovl-6, a long fatty acid elongase, contributes to de novo synthesis of fatty acids and regulates hepatic insulin sensitivity. Hepatic regulation of Elovl-6 gene expression in various nutritional conditions suggested that, like other lipogenic enzyme genes, Elovl-6 is a target of SREBP-1, a transcription factor governing fatty acid synthesis. Supportively, adenoviral RNAi knockdown of SREBP-1 in mouse liver suppressed Elovl-6 mRNA and fatty acid synthase levels. Therefore, we analyzed mouse Elovl-6 gene promoter to determine its role as an SREBP-1 target. Luciferase reporter assays of 1.4-kb 5′ flanking region of mouse Elovl-6 gene in HepG2 cells demonstrated that nuclear SREBPs activated the Elovl-6 promoter, highlighting two SREBP binding sites: proximal SRE-1 and distal SRE-2. EMSA indicated that SRE-1 had higher affinity than SRE-2 for SREBP. ChIP assays confirmed in vivo binding of hepatic nuclear SREBP-1c protein. These data demonstrated that Elovl-6 is regulated directly and primarily by SREBP-1c.