The chaperone-like protein HYPK acts together with NatA in cotranslational N-terminal acetylation and prevention of Huntingtin aggregation.
The human NatA protein N(alpha)-terminal-acetyltransferase complex is responsible for cotranslational N-terminal acetylation of proteins with Ser, Ala, Thr, Gly, and Val N termini. The NatA complex is composed of the catalytic subunit hNaa10p (hArd1) and the auxiliary subunit hNaa15p (hNat1/NATH). Using immunoprecipitation coupled with mass spectrometry, we identified endogenous HYPK, a Huntingtin (Htt)-interacting protein, as a novel stable interactor of NatA. HYPK has chaperone-like properties preventing Htt aggregation. HYPK, hNaa10p, and hNaa15p were associated with polysome fractions, indicating a function of HYPK associated with the NatA complex during protein translation. Knockdown of both hNAA10 and hNAA15 decreased HYPK protein levels, possibly indicating that NatA is required for the stability of HYPK. The biological importance of HYPK was evident from HYPK-knockdown HeLa cells displaying apoptosis and cell cycle arrest in the G(0)/G(1) phase. Knockdown of HYPK or hNAA10 resulted in increased aggregation of an Htt-enhanced green fluorescent protein (Htt-EGFP) fusion with expanded polyglutamine stretches, suggesting that both HYPK and NatA prevent Htt aggregation. Furthermore, we demonstrated that HYPK is required for N-terminal acetylation of the known in vivo NatA substrate protein PCNP. Taken together, the data indicate that the physical interaction between HYPK and NatA seems to be of functional importance both for Htt aggregation and for N-terminal acetylation.
Department of Molecular Biology, University of Bergen, Thormøhlensgate 55, N-5020 Bergen, Norway. Thomas.Arnesen@mbi.uib.no
Thomas
T
Arnesen
Kristian K
KK
Starheim
Petra
P
Van Damme
Rune
R
Evjenth
Huyen
H
Dinh
Matthew J
MJ
Betts
Anita
A
Ryningen
Joël
J
Vandekerckhove
Kris
K
Gevaert
Dave
D
Anderson
D000107:Acetylation; D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D001191:Arylamine N-Acetyltransferase / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D002460:Cell Line; D055785:Gene Knockdown Techniques; D006801:Humans; D000071058:Huntingtin Protein; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D063209:N-Terminal Acetyltransferase A; D063213:N-Terminal Acetyltransferase E; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C086055:HTT protein, human; C526912:HYPK protein, human; D000071058:Huntingtin Protein; D007527:Isoenzymes; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C465618:PCNP protein, human; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D000123:Acetyltransferases; D063209:N-Terminal Acetyltransferase A; C504824:NAA10 protein, human; D063213:N-Terminal Acetyltransferase E; D001191:Arylamine N-Acetyltransferase; C089384:N-acetyltransferase 1