RESUMO
Acetyl-CoA carboxylase (ACC) exists as two major isoforms originated from separate genes: ACCalpha (or ACC1) and ACCbeta (or ACC2). Previous data revealed that ACCbeta has two forms of mRNA with different 5'-untranslated regions derived by different usage of promoters, I and II, in human. In this study, we revealed that ACCbeta expression in liver is markedly stimulated by food intake at the transcriptional level. In the process of this induction in rat liver, promoter II plays the major role in regulating the expression of ACCbeta gene. The transient transfection with promoter II-luciferase reporters elucidated that the region from -93 to -38 nucleotides is important for the responsiveness to sterol regulatory element-binding protein-1 (SREBP-1), which is known to be the principle mediator for the stimulation of gene transcriptions by insulin and diet. The Sp1-binding site (-71 to -66) and neighboring two conserved SREs (-62 to -44) play a critical role in the stimulation of ACCbeta gene expression by SREBP-1. In vivo chromatin immunoprecipitation assay revealed that SREBP-1 directly bound to ACCbeta promoter II in liver, and its binding was regulated by the diet. This study provides evidence that ACCbeta expression in liver is regulated at the transcriptional level by the direct interaction of SREBP-1 with promoter II.
