ATF6α stimulates cholesterogenic gene expression and de novo cholesterol synthesis

The activating transcription factor 6α (ATF6α) is a sensor of the endoplasmic reticulum stress response that regulates the expression of genes involved in the unfolded protein response. Here we found that forced expression of a constitutively active form of ATF6α, ATF6(N), stimulated the expression of cholesterogenic genes, including 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase, HMG-CoA synthase, and squalene synthase, and de novo cholesterol synthesis in hepatoma Huh-7 cells. An ATF6α mutant lacking the DNA-binding domain ATF6(N)ΔbZip failed to show these effects. Luciferase assays indicated that ATF6(N) overexpression stimulated the promoter activities of HMG-CoA reductase, HMG-CoA synthase, and squalene synthase. Chromatin immunoprecipitation assays revealed that ATF6(N) interacted with the promoter region of the HMG-CoA synthase gene. Collectively, these results indicate that ATF6α can regulate de novo cholesterol synthesis through stimulation of cholesterogenic gene expression.