Noncanonical function of epigenetic reader YTHDF1 inhibits MASLD progression by maintaining peroxisomes and...

YTH N⁶-methyladenosine RNA binding protein F1 (YTHDF1) enables N⁶-methyladenosine-containing RNA binding activity, involved in mRNA destabilization and positive regulation of translational initiation. Here we aimed to investigate the main molecular events associated with YTHDF1 during the course of metabolic dysfunction-associated steatotic liver disease (MASLD). YTHDF1 expression was detected by western blotting and real-time PCR. Ythdf1 hepatocyte-specific knockout mice were generated in this study. RNA sequencing and proteomic analyses were performed to investigate potentially involved molecular pathways. The protein levels of YTHDF1 were increased during MASLD progression. Under high-fat diet intervention, hepatocyte-specific Ythdf1-knockout mice exhibited a pronounced increase in both liver weight and liver-to-body weight ratio, accompanied by significant hepatic steatosis. YTHDF1 depletion promotes the progression of MASLD through enhanced peroxisome activation and mitochondria dysfunction, which are independent of its RNA N⁶-methyladenosine reader activity. In particular, decreased YTHDF1 enhances the expression of acyl-CoA oxidase 1 (ACOX1), and peroxisome activation in a manner relies on YTHDF1 facilitating the formation of stress granules in MASLD. In addition, YTHDF1 was localized in the mitochondria and interacted with SLC25A11, affecting mitochondrial glutathione transport and its homeostasis. Finally, the identified lysine 191 methylation modification can reduce the stability of YTHDF1 protein, thereby achieving its protein expression regulation during MASLD progression. YTHDF1 inhibits MASLD progression by modulating stress granule sequestration of ACOX1 mRNA and maintaining mitochondrial homeostasis.