title: Knockdown of human N alpha-terminal acetyltransferase complex C leads to p53-dependent apoptosis and aberrant human Arl8b localization.
abstract: Protein N(alpha)-terminal acetylation is one of the most common protein modifications in eukaryotic cells. In yeast, three major complexes, NatA, NatB, and NatC, catalyze nearly all N-terminal acetylation, acetylating specific subsets of protein N termini. In human cells, only the NatA and NatB complexes have been described. We here identify and characterize the human NatC (hNatC) complex, containing the catalytic subunit hMak3 and the auxiliary subunits hMak10 and hMak31. This complex associates with ribosomes, and hMak3 acetylates Met-Leu protein N termini in vitro, suggesting a model in which the human NatC complex functions in cotranslational N-terminal acetylation. Small interfering RNA-mediated knockdown of NatC subunits results in p53-dependent cell death and reduced growth of human cell lines. As a consequence of hMAK3 knockdown, p53 is stabilized and phosphorylated and there is a significant transcriptional activation of proapoptotic genes downstream of p53. Knockdown of hMAK3 alters the subcellular localization of the Arf-like GTPase hArl8b, supporting that hArl8b is a hMak3 substrate in vivo. Taken together, hNatC-mediated N-terminal acetylation is important for maintenance of protein function and cell viability in human cells.
authors.affiliation: Department of Molecular Biology, University of Bergen, Thormøhlensgate 55, N-5020 Bergen, Norway.
authors.forename: Kristian K
authors.initials: KK
authors.lastname: Starheim
authors.forename: Darina
authors.initials: D
authors.lastname: Gromyko
authors.forename: Rune
authors.initials: R
authors.lastname: Evjenth
authors.forename: Anita
authors.initials: A
authors.lastname: Ryningen
authors.forename: Jan Erik
authors.initials: JE
authors.lastname: Varhaug
authors.forename: Johan R
authors.initials: JR
authors.lastname: Lillehaug
authors.forename: Thomas
authors.initials: T
authors.lastname: Arnesen
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D055785:Gene Knockdown Techniques; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D063211:N-Terminal Acetyltransferase C; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: C511801:ARL8B protein, human; D007527:Isoenzymes; D009097:Multienzyme Complexes; D021122:Protein Subunits; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D000123:Acetyltransferases; D063211:N-Terminal Acetyltransferase C; C570950:NAA30 protein, human; D020727:ADP-Ribosylation Factors