Nα-terminal acetylation of proteins by NatA and NatB serves distinct physiological roles in Saccharomyces cerevisiae

SO_SCPLOWUMMARYC_SCPLOWN-terminal (Nt)-acetylation is a highly prevalent co-translational protein modification in eukaryotes, catalyzed by at least five Nt-acetyltransferases (Nat) with differing specificities. Nt-acetylation has been implicated in protein quality control but its broad biological significance remains elusive. We investigated the roles of the two major Nats of S. cerevisiae, NatA and NatB, by performing transcriptome, translatome and proteome profiling of natA{Delta} and natB{Delta} mutants. Our results do not support a general role of Nt-acetylation in protein degradation but reveal an unexpected range of Nat-specific phenotypes. NatA is implicated in systemic adaptation control, as natA{Delta} mutants display altered expression of transposons, sub-telomeric genes, pheromone response genes and nuclear genes encoding mitochondrial ribosomal proteins. NatB predominantly affects protein folding, as natB{Delta} mutants accumulate protein aggregates, induce stress responses and display reduced fitness in absence of the ribosome-associated chaperone Ssb. These phenotypic differences indicate that controlling Nat activities may serve to elicit distinct cellular responses.