ASCH Domain-Containing Proteins Act as tRNA N 4 -acetylcytidine Erasers

ABSTRACT N 4 -acetylcytidine (ac 4 C) is a conserved RNA modification that enhances RNA stability and translation accuracy. Emerging evidence suggests that ac 4 C levels can change in response to cellular and environmental triggers. Despite these indications of regulatory dynamics, the enzymes responsible for removing ac 4 C, beyond the recently proposed rRNA deacetylase SIRT7, remain largely unknown. Here, we examined 19 ASCH domain-containing proteins from bacteria, archaea, and humans to determine their possible activity in tRNA deacetylation. Despite differences in their sequences, structures, and nucleic-acid binding properties, all tested proteins were capable of removing ac 4 C from tRNA, revealing a conserved deacetylase activity across diverse species. The proteins were found to vary in nucleic acid recognition, including an archaeal specific helix–turn–helix domain that promotes strong tRNA binding. Together, these findings establish ASCH proteins as a widespread and previously unrecognized family of tRNA deacetylases, suggesting that enzymatic ac 4 C turnover may require complex regulation within the cells. GRAPHICAL ABSTRACT