LAUSR

As the first identified N6‐methyladenosine (m6A) demethylase, fat mass and obesity‐associated (FTO) protein is associated with fatty acid synthase (FASN) and lipid accumulation. However, little is known about the regulatory role of FTO in the expression of FASN and de novo lipogenesis through m6A modification. In this study, we used FTO small interfering RNA to explore the effects of FTO knockdown on hepatic lipogenesis and its underlying epigenetic mechanism in HepG2 cells. We found that knockdown of FTO increased m6A levels in total RNA and enhanced the expression of YTH domain family member 2 which serves as the m6A‐binding protein. The de novo lipogenic enzymes and intracellular lipid content were significantly decreased under FTO knockdown. Mechanistically, knockdown of FTO dramatically enhanced m6A levels in FASN messenger RNA (mRNA), leading to the reduced expression of FASN mRNA through m6A‐mediated mRNA decay. The protein expressions of FASN along with acetyl CoA carboxylase and ATP‐citrate lyase were further decreased, which inhibited de novo lipogenesis, thereby resulting in the deficiency of lipid accumulation in HepG2 cells and the induction of cellular apoptosis. The results reveal that FTO regulates hepatic lipogenesis via FTO‐dependent m6A demethylation in FASN mRNA and indicate the critical role of FTO‐mediated lipid metabolism in the survival of HepG2 cells. This study provides novel insights into a unique RNA epigenetic mechanism by which FTO mediates hepatic lipid accumulation through m6A modification and indicates that FTO could be a potential target for obesity‐related diseases and cancer.