Dynamic RNA acetylation revealed by quantitative cross-evolutionary mapping.

N-acetylcytidine (acC) is an ancient and highly conserved RNA modification that is present on tRNA and rRNA and has recently been investigated in eukaryotic mRNA. However, the distribution, dynamics and functions of cytidine acetylation have yet to be fully elucidated. Here we report acC-seq, a chemical genomic method for the transcriptome-wide quantitative mapping of acC at single-nucleotide resolution. In human and yeast mRNAs, acC sites are not detected but can be induced-at a conserved sequence motif-via the ectopic overexpression of eukaryotic acetyltransferase complexes. By contrast, cross-evolutionary profiling revealed unprecedented levels of acC across hundreds of residues in rRNA, tRNA, non-coding RNA and mRNA from hyperthermophilic archaea. AcC is markedly induced in response to increases in temperature, and acetyltransferase-deficient archaeal strains exhibit temperature-dependent growth defects. Visualization of wild-type and acetyltransferase-deficient archaeal ribosomes by cryo-electron microscopy provided structural insights into the temperature-dependent distribution of acC and its potential thermoadaptive role. Our studies quantitatively define the acC landscape, providing a technical and conceptual foundation for elucidating the role of this modification in biology and disease.