Methylation at the 6 position of adenosine (m6A) in RNA is rapidly and transiently induced at DNA damage sites in response to ultraviolet irradiation. UV light can damage DNA and be a threat to cell survival. The cells respond to this threat by identifying DNA lesions, excising the affected nucleotides and synthesizing new DNA at the site of damage. Yang Shi and colleagues report that polyadenylated RNAs—RNAs to which a tail of adenosines has been added as part of their maturation into functional messenger RNAs—undergo a specific modification when they are close to DNA that has been damaged by UV light. This modification, which consists in the addition of a methyl group to the N6 position of adenosine, is promoted by the METTL3 methyltransferase and suppressed by the FTO demethylase. This RNA modification regulates the DNA repair process, which is delayed in the absence of METTL3. Importantly, the modification helps to recruit the trans-lesion repair DNA polymerase, pol κ, to the damaged DNA site. This study uncovers a new cellular role for this RNA modification. Cell proliferation and survival require the faithful maintenance and propagation of genetic information, which are threatened by the ubiquitous sources of DNA damage present intracellularly and in the external environment. A system of DNA repair, called the DNA damage response, detects and repairs damaged DNA and prevents cell division until the repair is complete. Here we report that methylation at the 6 position of adenosine (m6A) in RNA is rapidly (within 2 min) and transiently induced at DNA damage sites in response to ultraviolet irradiation. This modification occurs on numerous poly(A)+ transcripts and is regulated by the methyltransferase METTL3 (methyltransferase-like 3)1 and the demethylase FTO (fat mass and obesity-associated protein)2. In the absence of METTL3 catalytic activity, cells showed delayed repair of ultraviolet-induced cyclobutane pyrimidine adducts and elevated sensitivity to ultraviolet, demonstrating the importance of m6A in the ultraviolet-responsive DNA damage response. Multiple DNA polymerases are involved in the ultraviolet response, some of which resynthesize DNA after the lesion has been excised by the nucleotide excision repair pathway3, while others participate in trans-lesion synthesis to allow replication past damaged lesions in S phase4. DNA polymerase κ (Pol κ), which has been implicated in both nucleotide excision repair and trans-lesion synthesis5,6, required the catalytic activity of METTL3 for immediate localization to ultraviolet-induced DNA damage sites. Importantly, Pol κ overexpression qualitatively suppressed the cyclobutane pyrimidine removal defect associated with METTL3 loss. Thus, we have uncovered a novel function for RNA m6A modification in the ultraviolet-induced DNA damage response, and our findings collectively support a model in which m6A RNA serves as a beacon for the selective, rapid recruitment of Pol κ to damage sites to facilitate repair and cell survival.

RNA m6A methylation regulates the ultraviolet-induced DNA damage response