N 1 -methyladenosine methylome in messenger RNA and non-coding RNA.

Chemical modifications to rRNA, tRNA and mRNA provide a new regulatory layer of gene expression, which is termed as the `epitranscriptome'. N1 -methyladenosine (m1 A), first characterized more than 50 years ago, is a well-known modification in rRNA and tRNA. m1 A in these abundant non-coding RNAs plays important roles in maintaining their biological functions. Recent studies also reveal that m1 A is present in both nuclear-encoded and mitochondrial-encoded mRNA and is dynamically regulated by environmental and developmental conditions; m1 A is found in a subset of nuclear-encoded long non-coding RNAs as well. Finally, we also discuss the potential challenges of identifying m1 A modification in the human transcriptome.