Abstract

A critical question in genome stability is the nature of the chemical damage responsible for repair activation. We previously reported a novel pathway specifically activated during alkylation damage in human cells, where the E3 ubiquitin ligase RNF113A mediates the recruitment of the ASCC repair complex. Yet the mechanistic basis for the alkylation damage selectivity of this pathway remains unclear. Here, we demonstrate that RNA but not DNA alkylation is the initiating signal for this process. Aberrantly methylated RNA is sufficient to recruit ASCC, while an RNA dealkylase suppresses ASCC recruitment during chemical alkylation. This aberrant RNA methylation causes transcriptional repression in a manner dependent on the ASCC complex. We show that an alkylated pre-mRNA, or an RNA containing a single damaged base, is sufficient to activate RNF113A E3 activity in a phosphorylation-dependent manner. Together, our work identifies an unexpected role for RNA damage in eliciting a DNA repair response, and suggests that RNA may serve as the "canary in the coal mine" for sensing alkylation damage.