N(6)-methyladenosine Co-transcriptionally Directs The Demethylation Of Histone H3K9me2

m~6A represents a widespread modification of mRNA and lncRNA molecules,identified with a consensus motif of RRm~6ACH(R=G or A,H=A,C or U)conserved from yeast to human[1-3].m~6A is co-transcriptionally generated by the METTL3-METTL14 core methyltransferase complex[4-6],and erased by demethylases FTO/ALKBH5[2,7].m~6A can be recognized by proteins with YTH domains to regulates many post-transcriptional processes,and loss of it disrupts various critical biological processes[8].Accumulating evidence reveals that the transcription process regulates chromatin dynalics[9,10].The biogenesis of m~6A in a co-transcriptional manner has beel well appreciated[5,6],but its direct regulation on chromatin remains largely unknown.A dynamic epigenome is critical for appropriate gene expression in development and health[11-15].Central to this is the intricate process of transcription[10,16-20],which integrates cellular signaling with chromatin changes,transcriptional machinery,and modifications to mRNA,such as N(6)-methyladenosine(m~6A),which is co-transcriptionally incorporated.The integration of these aspects of the dynamic epigenome,however,is not well understood mechanistically.Based on this,we studied the relationship between histone modification and 1RNA mtA which is co-transcriptionally incorporated.Firstly,we established a reporter system to screen histone modificaions,and found that when m~6A was modified on the transcripts,the silence histone modification marker H3K9me2 would be specifically removed on the related chromatin regions.Other histone modificaions had little change.Then we constructed the mutant and knockdown cell lines of METTL3 and METTL14,and found that the level of H3K9me2 globally increased.It represents that METTL3/METTL14,the core methyltransferase of m~6A,can regulate histone H3K9me2 modification.To further clarify whether methyltransferase or m~6A regulates H3K9me2,we established METTL3 enzyme inactive cell line,and found that the level of H3K9me2 also increased globally,suggesting that m~6A can regulate histone modification H3K9me2.Then we observed a genome-wide correlation between m~6A,METTL3 and occupancy by the H3K9me2 demethylase KDM3B through MeRIP-seq and ChIP-seq.Furthermore,we confirmed that m~6A reader YTHDC1 physically interacts and recruits KDM3B to m~6A-associated chromatin regions,promoting H3K9me2 demethylation and gene expression through Co-IP,ChIP-seq and dPspCas13b-targeting assay.Finally,we found that m~6A can promote the expression of genes mediated by H3K9me2 through RNA-seq and Pol ?ChIP-seq.In a word,This study establishes a direct link between m~6A and dynamic chromatin modification,provides mechanistic insight into the co-transcriptional interplay between RNA modification and histone modifications,integrates RNA m~6A,histone modification and transcriptional regulation and plays an important role in the field of RNA modification.