title: The human N-alpha-acetyltransferase 40 (hNaa40p/hNatD) is conserved from yeast and N-terminally acetylates histones H2A and H4.
abstract: Protein N(α)-terminal acetylation (Nt-acetylation) is considered one of the most common protein modification in eukaryotes, and 80-90% of all soluble human proteins are modified in this way, with functional implications ranging from altered protein function and stability to translocation potency amongst others. Nt-acetylation is catalyzed by N-terminal acetyltransferases (NATs), and in yeast five NAT types are identified and denoted NatA-NatE. Higher eukaryotes additionally express NatF. Except for NatD, human orthologues for all yeast NATs are identified. yNatD is defined as the catalytic unit Naa40p (Nat4) which co-translationally Nt-acetylates histones H2A and H4. In this study we identified and characterized hNaa40p/hNatD, the human orthologue of the yeast Naa40p. An in vitro proteome-derived peptide library Nt-acetylation assay indicated that recombinant hNaa40p acetylates N-termini starting with the consensus sequence Ser-Gly-Gly-Gly-Lys-, strongly resembling the N-termini of the human histones H2A and H4. This was confirmed as recombinant hNaa40p Nt-acetylated the oligopeptides derived from the N-termini of both histones. In contrast, a synthetically Nt-acetylated H4 N-terminal peptide with all lysines being non-acetylated, was not significantly acetylated by hNaa40p, indicating that hNaa40p catalyzed H4 N(α)-acetylation and not H4 lysine N(ε)-acetylation. Also, immunoprecipitated hNaa40p specifically Nt-acetylated H4 in vitro. Heterologous expression of hNaa40p in a yeast naa40-Δ strain restored Nt-acetylation of yeast histone H4, but not H2A in vivo, probably reflecting the fact that the N-terminal sequences of human H2A and H4 are highly similar to each other and to yeast H4 while the N-terminal sequence of yeast H2A differs. Thus, Naa40p seems to have co-evolved with the human H2A sequence. Finally, a partial co-sedimentation with ribosomes indicates that hNaa40p co-translationally acetylates H2A and H4. Combined, our results strongly suggest that human Naa40p/NatD is conserved from yeast. Thus, the NATs of all classes of N-terminally acetylated proteins in humans now appear to be accounted for.
authors.affiliation: Department of Molecular Biology, University of Bergen, Bergen, Norway.
authors.forename: Kristine
authors.initials: K
authors.lastname: Hole
authors.forename: Petra
authors.initials: P
authors.lastname: Van Damme
authors.forename: Monica
authors.initials: M
authors.lastname: Dalva
authors.forename: Henriette
authors.initials: H
authors.lastname: Aksnes
authors.forename: Nina
authors.initials: N
authors.lastname: Glomnes
authors.forename: Jan Erik
authors.initials: JE
authors.lastname: Varhaug
authors.forename: Johan R
authors.initials: JR
authors.lastname: Lillehaug
authors.forename: Kris
authors.initials: K
authors.lastname: Gevaert
authors.forename: Thomas
authors.initials: T
authors.lastname: Arnesen
mesh_terms: D000107:Acetylation; D000123:Acetyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D006657:Histones / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D063212:N-Terminal Acetyltransferase D; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D015003:Yeasts / Q000201:enzymology*
chemical_list: D006657:Histones; D000123:Acetyltransferases; D063212:N-Terminal Acetyltransferase D; C523773:NAA40 protein, human