m A deposition is regulated by PRMT1-mediated arginine methylation of METTL14 in its disordered C-terminal region.

The N6-methyladenosine (m A) RNA modification serves crucial functions in RNA metabolism; however, the molecular mechanisms underlying the regulation of m A are not well understood. Here, we establish arginine methylation of METTL14, a component of the m A methyltransferase complex, as a novel pathway that controls m A deposition in mammalian cells. 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 RNA polymerase II (RNAPII). Mouse embryonic stem cells (mESCs) expressing arginine methylation-deficient METTL14 exhibit significantly reduced global m A levels. Transcriptome-wide m A analysis identified 1,701 METTL14 arginine methylation-dependent m A sites located in 1,290 genes involved in various cellular processes, including stem cell maintenance and DNA repair. These arginine methylation-dependent m A sites are associated with enhanced 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 m A regulation and new functions of arginine methylation in RNA metabolism.