RNA epigenetics--chemical messages for posttranscriptional gene regulation.

Chemical modifications in cellular RNA are diverse and abundant. Commonly found in ribosomal RNA (rRNA), transfer RNA (tRNA), long-noncoding RNA (lncRNA), and small nuclear (snRNA), these components play various structural and functional roles. Until recently, the roles of chemical modifications within messenger RNA (mRNA) have been understudied. Recent maps of several mRNA modifications have suggested regulatory functions for these marks. This review summarizes recent advances in identifying and understanding biological roles of posttranscriptional mRNA modification, or ‘RNA epigenetics’, with an emphasis on the most common internal modification of eukaryotic mRNA, N 6 -methyladenosine (m 6 A). We also discuss YTH proteins as direct mediators of m 6 A function and the emerging role of this mark in a new layer of gene expression regulation.