A Unified Model for the Function of YTHDF Proteins in Regulating m6A-Modified mRNA

N 6 -methyladenosine (m 6 A) is the most abundant mRNA nucleotide modification and regulates critical aspects of cellular physiology and differentiation. m 6 A is thought to mediate its effects through a complex network of interactions between different m 6 A sites and three functionally distinct cytoplasmic YTHDF m 6 A-binding proteins (DF1, DF2, and DF3). In contrast to the prevailing model, we show that DF proteins bind the same m 6 A-modified mRNAs rather than different mRNAs. Furthermore, we find that DF proteins do not induce translation in HeLa cells. Instead, the DF paralogs act redundantly to mediate mRNA degradation and cellular differentiation. The ability of DF proteins to regulate stability and differentiation becomes evident only when all three DF paralogs are depleted simultaneously. Our study reveals a unified model of m 6 A function in which all m 6 A-modified mRNAs are subjected to the combined action of YTHDF proteins in proportion to the number of m 6 A sites.