N⁶-methyladenosine (m⁶A) is the most abundant internal RNA modifications in mammals and best established epitranscriptomic mark. Despite the development of various tools to map m⁶A, a transcriptome-wide method that enables absolute quantification of m⁶A at the base-resolution is lacking. Here, we develop such a method “GLORI”, based on chemical-mediated deamination of unmethylated adenosines; thus, GLORI is conceptually similar to the detection and quantification of DNA 5-methylcytosine via bisulfite sequencing. Using GLORI, we obtain a quantitative m⁶A methylome in mouse and human cells, and reveal clustered m⁶A modifications with differential distribution and stoichiometry. In addition, we characterize the m⁶A dynamics upon stress conditions and provide a quantitative landscape of m⁶A modification in gene expression regulation. Collectively, GLORI is an unbiased and convenient method for absolute quantification of m⁶A methylome in biology.
 

m6A, quantification, sequencing, epitranscriptome