Atypical K6-linked ubiquitylation marks toxic RNA-protein crosslinks induced by formaldehyde

Reactive aldehydes are produced during cellular metabolism and can accumulate in specific tissues particularly when aldehyde clearance mechanisms are impaired. Reactive aldehydes induce DNA-DNA and DNA-protein crosslinks (DPCs) that are repaired by different DNA repair pathways. Cellular toxicity of endogenous formaldehyde has been attributed to the damage of the genomic DNA and consequent inhibition of transcription. However, whether damage to other cellular macromolecules and interference with additional metabolic processes contributes to formaldehyde toxicity has not been investigated. We demonstrate that formaldehyde induces toxic RNA-protein crosslinks (RPCs) in mRNA that inhibit translation and induce a specific RPC stress response pathway that is characterized by linkage-specific ubiquitylation. RPCs in the mRNA are recognized by stalling ribosomes and marked by K6-linked ubiquitylation that promotes their clearance by the ubiquitin-dependent unfoldase VCP. Overall design: Comparative gene expression profiling analysis of factory-RNA-seq data for U2OS cells without (DMSO) or with FA treatment (PFA).