Arginine methylation of the intrinsically disordered C-terminus of METTL14 controls N6-methyladenosine function in DNA repair

The N6-methyladenosine (m6A) RNA modification serves crucial functions in RNA metabolism; however, the molecular mechanisms underlying the regulation of m6A are not well understood. Here, we establish arginine methylation of METTL14, a component of the m6A methyltransferase complex, as a novel pathway that controls the function of m6A in DNA repair. Specifically, protein arginine methyltransferase 1 (PRMT1) interacts with and methylates the intrinsically disordered C-terminus of METTL14, which promotes its interaction with RNA substrates, enhances its RNA methylation activity, and is crucial for its interaction with RNAPII. Mouse embryonic stem cells (mESCs) expressing arginine methylation-deficient METTL14 exhibit dramatically reduced global m6A levels. Transcriptome-wide m6A analysis reveals that arginine methylation-dependent m6A enhances the translation of genes essential for the repair of DNA interstrand crosslinks; thus, METTL14 arginine methylation-deficient mESCs are hypersensitive to DNA crosslinking agents. Collectively, these findings reveal important aspects of m6A regulation that could have broad implications in normal development and in diseases such as cancer. Overall design: Using a modified m6A-seq protocol (Dominissini et al., 2013), we profiled the genome-wide m6A methylomes of WT, Mettl14 KO, KO+WT, KO+5RK, and KO+13RK mESCs. For each sample, we analyzed three experimental replicates using both RIP-seq with an m6A-specific antibody and standard RNA-seq of the input control.