The human N-alpha-acetyltransferase 40 (hNaa40p/hNatD) is conserved from yeast and N-terminally acetylates histones H2A and H4.

Department of Molecular Biology, University of Bergen, Bergen, Norway.
PLoS ONE (Impact Factor: 3.73). 01/2011; 6(9):e24713. DOI:10.1371/journal.pone.0024713
Source: PubMed

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.

0 0
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Post-translational modifications of histones play a key role in DNA-based processes, like transcription, by modulating chromatin structure. N-terminal acetylation is unique among the numerous histone modifications because it is deposited on the N-alpha amino group of the first residue instead of the side-chain of amino acids. The function of this modification and its interplay with other internal histone marks has not been previously addressed. Here, we identified N-terminal acetylation of H4 (N-acH4) as a novel regulator of arginine methylation and chromatin silencing in Saccharomyces cerevisiae. Lack of the H4 N-alpha acetyltransferase (Nat4) activity results specifically in increased deposition of asymmetric dimethylation of histone H4 arginine 3 (H4R3me2a) and in enhanced ribosomal-DNA silencing. Consistent with this, H4 N-terminal acetylation impairs the activity of the Hmt1 methyltransferase towards H4R3 in vitro. Furthermore, combinatorial loss of N-acH4 with internal histone acetylation at lysines 5, 8 and 12 has a synergistic induction of H4R3me2a deposition and rDNA silencing that leads to a severe growth defect. This defect is completely rescued by mutating arginine 3 to lysine (H4R3K), suggesting that abnormal deposition of a single histone modification, H4R3me2a, can impact on cell growth. Notably, the cross-talk between N-acH4 and H4R3me2a, which regulates rDNA silencing, is induced under calorie restriction conditions. Collectively, these findings unveil a molecular and biological function for H4 N-terminal acetylation, identify its interplay with internal histone modifications, and provide general mechanistic implications for N-alpha-terminal acetylation, one of the most common protein modifications in eukaryotes.
    PLoS Genetics 09/2013; 9(9):e1003805. · 8.52 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: N-terminal acetylation is ubiquitous among eukaryotic proteins and controls a myriad of biological processes. Of the N-terminal acetyltransferases (NATs) that facilitate this cotranslational modification, the heterodimeric NatA complex has the most diversity for substrate selection and modifies the majority of all N-terminally acetylated proteins. Here, we report the X-ray crystal structure of the 100-kDa holo-NatA complex from Schizosaccharomyces pombe, in the absence and presence of a bisubstrate peptide-CoA-conjugate inhibitor, as well as the structure of the uncomplexed Naa10p catalytic subunit. The NatA-Naa15p auxiliary subunit contains 13 tetratricopeptide motifs and adopts a ring-like topology that wraps around the NatA-Naa10p subunit, an interaction that alters the Naa10p active site for substrate-specific acetylation. These studies have implications for understanding the mechanistic details of other NAT complexes and how regulatory subunits modulate the activity of the broader family of protein acetyltransferases.
    Nature Structural & Molecular Biology 08/2013; · 11.90 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: The Arg/N-end rule pathway targets for degradation proteins that bear specific unacetylated N-terminal residues while the Ac/N-end rule pathway targets proteins through their N(α)-terminally acetylated (Nt-acetylated) residues. Here, we show that Ubr1, the ubiquitin ligase of the Arg/N-end rule pathway, recognizes unacetylated N-terminal methionine if it is followed by a hydrophobic residue. This capability of Ubr1 expands the range of substrates that can be targeted for degradation by the Arg/N-end rule pathway because virtually all nascent cellular proteins bear N-terminal methionine. We identified Msn4, Sry1, Arl3, and Pre5 as examples of normal or misfolded proteins that can be destroyed through the recognition of their unacetylated N-terminal methionine. Inasmuch as proteins bearing the Nt-acetylated N-terminal methionine residue are substrates of the Ac/N-end rule pathway, the resulting complementarity of the Arg/N-end rule and Ac/N-end rule pathways enables the elimination of protein substrates regardless of acetylation state of N-terminal methionine in these substrates.
    Cell 12/2013; · 31.96 Impact Factor

Full-text (2 Sources)

Available from
May 22, 2013