Human Naa30 Can Rescue Yeast Mak3 Delta Mutant Growth Phenotypes

N-terminal acetylation is a common protein modification defined by the addition of an acetyl group to the start of a protein [1?3]. Current estimates suggest that -80% of human proteins and -50?70% of yeast proteins are to varying degrees N-terminally acetylated [1,4?6].N-terminal acetylation was discovered more than 60 years ago [7] and its biological significance is becoming increasingly prevalent in many areas of biomedicine. From a clinical perspective, dysregulated N-terminal acetylation can be causative factor of intellectual disability, autism spectrum disorder, and congenital heart disease [8?11]. These clinABSTRACT N-terminal acetylation is an irreversible protein modification that primarily occurs co-translationally, and is catalyzed by a highly conserved family of N-terminal acetyltransferases (NATs). The NatC complex (NAA30?NAA35?NAA38) is a major NAT enzyme, which was first described in yeast and estimated to N-terminally acetylate -20% of the proteome. The activity of NatC is crucial for the correct functioning of its substrates, which include translocation to the Golgi apparatus, the inner nuclear membrane as well as proper mitochondrial function. We show in comparative viability and growth assays that yeast cells lacking MAK3/NAA30 grow poorly in non-fermentable carbon sources and other stress conditions. By using two different experimental approaches and two yeast strains, we show that liquid growth assays are the method of choice when analyzing subtle growth defects, keeping loss of information to a minimum. We further demonstrate that human NAA30 can functionally replace yeast MAK3/NAA30. However, this depends on the genetic background of the yeast strain. These findings indicate that the function of MAK3/NAA30 is evolutionarily conserved from yeast to human. Our yeast system provides a powerful approach to study potential human NAA30 variants using a high-throughput liquid growth assay with various stress conditions.