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Elsevier, Molecular and Cellular Proteomics, 8(13), p. 2031-2041, 2014

DOI: 10.1074/mcp.m113.035402

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A Saccharomyces cerevisiae Model Reveals In Vivo Functional Impairment of the Ogden Syndrome N-Terminal Acetyltransferase NAA10 Ser37Pro Mutant

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

N-terminal acetylation (Nt-acetylation) occurs on the majority of eukaryotic proteins and is catalysed by N-terminal acetyltransferases (NATs). Nt-acetylation is increasingly recognized as a vital modification with functional implications ranging from protein degradation to protein localization. Very recently, the first human genetic disorder caused by a mutation in a NAT gene was reported; boys diagnosed with the X-linked Ogden syndrome harbour a p.Ser37Pro (S37P) mutation in the gene encoding Naa10, the catalytic subunit of the NatA complex, and suffer from global developmental delays and lethality during infancy. Here, we describe a Saccharomyces cerevisiae model developed by introducing the human wild-type or mutant NatA complex into yeast lacking NatA (NatA-). The wild-type human NatA complex phenotypically complemented the NatA- strain, while only a partial rescue was observed for the Ogden mutant NatA complex suggesting that hNaa10 S37P is only partially functional in vivo. Immunoprecipitation experiments revealed a reduced subunit complexation for the mutant hNatA S37P next to a reduced in vitro catalytic activity. We performed quantitative Nt-acetylome analyses on a control yeast strain (yNatA), a yeast NatA deletion strain (yNatA-), a yeast NatA deletion strain expressing wild-type human NatA (hNatA), and a yeast NatA deletion strain expressing mutant human NatA (hNatA S37P). Interestingly, a generally reduced degree of Nt-acetylation was observed among a large group of NatA substrates in the yeast expressing mutant hNatA as compared to yeast expressing wild-type hNatA. Combined, these data provide strong support for the functional impairment of hNaa10 S37P in vivo and suggest that reduced Nt-acetylation of one or more target substrates contributes to the pathogenesis of the Ogden syndrome. Comparative analysis between human and yeast NatA also provided new insights into the co-evolution of the NatA complexes and their substrates. For instance, (Met-)Ala- N-termini are more prevalent in the human proteome as compared to the yeast proteome, and hNatA displays a preference towards these N-termini as compared to yNatA.