N1-methyladenine safeguards against aberrant RNA-protein association during proteostasis stress
Post-transcriptional modifications of nucleotide bases can effect several aspects of mRNA function. For example, the recent work has established the role of m6A in the coordinated regulation of transcriptome turnover and translation during cellular differentiation and tumorigenesis. The levels of m1A in mRNAs reach up to 10% of those of m6A, yet the functional consequences of this modification are much less clear. Here we show that N1-methyladenine protects mRNAs against aberrant interactions during heat shock and amyloidogenesis in mammalian cells. The m1A methylation motif correlated with the enhanced sequestration of transcripts in stress granules (SG). The cognate methyltransferase TRMT6/61A accumulated and m1A was enriched in SG. Downregulation of the catalytic subunit TRMT61A enhanced amyloidogenesis in the cytosol and increased bystander protein and RNA co-aggregation with A{beta} aggregates. Faulty granulation of mutant RNAs has been implicated in pathogenesis of protein aggregation disorders. Our results demonstrate that also normal mRNAs succumb to co-aggregation with proteins if RNA dynamics during stress is disturbed due to the insufficient N1-adenine methylation.