HYPK promotes the activity of the N ^α -acetyltransferase A complex to determine proteostasis of nonAc-X ² /N-degron–containing proteins

Abstract

In humans, the Huntingtin yeast partner K (HYPK) binds to the ribosome-associated N α -acetyltransferase A (NatA) complex that acetylates ~40% of the proteome in humans and Arabidopsis thaliana . However, the relevance of Hs HYPK for determining the human N-acetylome is unclear. Here, we identify the At HYPK protein as the first in vivo regulator of NatA activity in plants . At HYPK physically interacts with the ribosome-anchoring subunit of NatA and promotes N α -terminal acetylation of diverse NatA substrates. Loss-of- At HYPK mutants are remarkably resistant to drought stress and strongly resemble the phenotype of NatA-depleted plants. The ectopic expression of Hs HYPK rescues this phenotype. Combined transcriptomics, proteomics, and N-terminomics unravel that HYPK impairs plant metabolism and development, predominantly by regulating NatA activity. We demonstrate that HYPK is a critical regulator of global proteostasis by facilitating masking of the recently identified nonAc-X 2 /N-degron. This N-degron targets many nonacetylated NatA substrates for degradation by the ubiquitin-proteasome system.

A Natural History ofNAA15-related Neurodevelopmental Disorder Through Adolescence

“…Patient NAA15-011 was removed from the analysis due to their having performed much more poorly than the rest of their cohort. They had a de novo p.Asn864Ser pathogenic variant which is located in part of the region (residues 500-866 (Arnesen et al, 2010)) that interacts with the HYPK chaperone like protein which is important for NatA mediated acetylation and Huntingtin protein aggregation (Arnesen et al, 2010; Ghosh & Ranjan, 2022; Miklánková et al, 2022; Weyer et al, 2017). In addition to dysfunctional N-terminal acetylation being associated with neurodevelopmental delay, abnormal Huntingtin protein aggregation also can lead to cognitive decline (Alberti & Hyman, 2021; Liu et al, 2023; Soltani Khaboushan et al, 2023).…”

N-terminal acetylation can stabilize proteins independent of their ubiquitination

“…Consistently, a more recent study in human cell-lines showed that Nt-acetylated variants of the protein THOC7 had a substantially longer half-life than Nt-acetyl-free variants 14 . Furthermore, global quantitative mass spectrometry (MS) followed by targeted validation experiments in Arabidopsis thaliana indicated that in plant cells the majority of NatA substrates were destabilized by depletion of NatA, or of the NatA activating protein HYPK 15 , 16 . Similarly, loss of Nt-acetylation upon NatA deletion in yeast correlated with a significant reduction in turnover time of NatA substrates 17 .…”

NAA60 (HAT4): the newly discovered bi-functional Golgi member of the acetyltransferase family

“…In yeast, NatA is involved in adaptation control systems: mutations in NatA are followed by an alteration in the transposon system, in sub-telomeric genes and in genes responsible for pheromone response and encoding for mitochondrial and ribosomal proteins [ 62 ]. NatA complex contains NAA10 and NAA15 subunits and acetylates about 40% of the human proteome [ 63 ]. NatA interacts with the Huntingtin (Htt) yeast two-hybrid protein K (HYPK) protein [ 64 ].…”

“…NatA interacts with the Huntingtin (Htt) yeast two-hybrid protein K (HYPK) protein [ 64 ]. The NatA / HYPK complex has a dual role from which both proteins benefit: it prevents the Htt aggregation and strengthens the N-acetylase activity of NatA [ 65 ]. NatB predominantly regulates protein folding, and when it is mutated protein aggregation occurs; this event is recognized as a sign of cellular stress [ 66 ].…”

“…NatD downregulates transcriptional expression levels of Slug, a master regulator of epithelial–mesenchymal transition [ 67 ]. NatE activity is mediated via NAA50 or in complex with NAA10/NAA15 with HYPK [ 64 , 65 ].…”