METTL14 Regulates Chromatin Bivalent Domains in Mouse Embryonic Stem Cells [ChIP-seq]

METTL14 (methyltransferase-like 14) is an RNA binding protein that partners with METTL3 to mediate N6-methyladenosine (m6A) methylation of mRNA. Recent studies identified a function for METTL3 in heterochromatin and transcription, but the role of METTL14 in these contexts remains unclear. Here we show that METTL14 binds and regulates mouse embryonic stem cell bivalent domains, which are marked with tri-methylation at lysine 27 of histone H3 (H3K27me3) and tri-methylation at lysine 4 of histone H3 (H3K4me3). Knockout of Mettl14 results in decreased H3K27me3 but increased H3K4me3 levels at bivalent regions, resulting in the resolution of the bivalency and in increased transcription. We demonstrate that bivalent domain regulation by METTL14 is independent of METTL3 or m6A modification. Instead, METTL14 enhances H3K27me3 and reduces H3K4me3 by interacting with and probably recruiting the histone 3 lysine 27 (H3K27) methyltransferase complex PRC2 and the histone 3 lysine 4 (H3K4) demethylases KDM5B to chromatin. Our findings identify a METTL3-independent function of METTL14, important for maintaining the bivalent domains in mESCs, thus revealing a new mechanism of bivalent domain regulation in mammals. Overall design: Examination of METTL3 binding, METTL14 binding, PRC2 binding and histone modifications in Parental, METTL14 KO and rescue mESCs.