Methylglyoxal mutagenizes single-stranded DNA via Rev1-associated slippage and mispairing

Methylglyoxal (MG) is a highly reactive aldehyde that is produced endogenously during metabolism, and from exogenous sources like sugary food and cigarette smoke. Unless detoxified by glyoxalases, MG can readily react with DNA and proteins, generating characteristic glycation-derived lesions. As a result, MG exposure has been linked to a variety of human diseases, including cancers. Prior studies show that MG preferentially makes adducts on guanine residues, causing DNA damage. However, in vivo, how such events impact genome-wide MG mutagenicity is poorly understood. Such information is essential to comprehend the true contribution of MG to genome instability and global mutational burden. In the present study, we show that MG can robustly mutagenize single-stranded DNA in the yeast genome, within a guanine-centered mutable motif. We demonstrate that genome-wide MG mutagenesis is greatly elevated in the absence of the glyoxalase Glo1, and abrogated in the presence of the aldehyde quencher aminoguanidine. Importantly, we uncovered strand slippage and mispairing as the predominant mechanism for generation of all MG-associated mutations, and demonstrate that the translesion polymerase Rev1 is a key player in this pathway. Finally, we find that the primary MG-associated mutation is enriched in a variety of sequenced tumor datasets.