Transcriptome-Wide Detection of Internal N7-Methylguanosine.

m7G-seq detects internal 7-methylguanosine (m7G) sites within mRNAs and noncoding RNAs by misincorporation signatures. A chemical-assisted sequencing approach selectively converts internal m7G sites into abasic sites, triggering misincorporation at these sites in the presence of a specific reverse transcriptase. The further enrichment of m7G-induced abasic sites by biotin pull-down reveals hundreds of internal m7G sites in human mRNA. The misincorporation ratio before pull-down enrichment can be used for estimating the methylation fraction of some highly methylated m7G sites.