The rSjNAT13 protein induced high levels of anti-rSjNAT13 IgG antibodies. Transcript levels were highest in cercariae and 21-day-old worms, and higher in male adult worms than female adult worms. Real-time PCR analysis revealed SjNAT13 expression in all tested developmental stages. The 621 bp open reading frame of SjNAT13 encodes a polypeptide of 206 amino acids. In this study, a full-length complementary DNA (cDNA) encoding Schistosoma japonicum NAT13 (SjNAT13) was isolated from schistosome cDNAs. N-acetyltransferase 13 (NAT13) is a probable catalytic component of the ARD1A-NARG1 complex possessing alpha (N-terminal) acetyltransferase activity. This N-degron targets many nonacetylated NatA substrates for degradation by the ubiquitin-proteasome system. We demonstrate that HYPK is a critical regulator of global proteostasis by facilitating masking of the recently identified nonAc-X2/N-degron. Combined transcriptomics, proteomics, and N-terminomics unravel that HYPK impairs plant metabolism and development, predominantly by regulating NatA activity. The ectopic expression of HsHYPK rescues this phenotype. Loss-of-AtHYPK mutants are remarkably resistant to drought stress and strongly resemble the phenotype of NatA-depleted plants. AtHYPK physically interacts with the ribosome-anchoring subunit of NatA and promotes Nα-terminal acetylation of diverse NatA substrates. Here, we identify the AtHYPK protein as the first in vivo regulator of NatA activity in plants. However, the relevance of HsHYPK for determining the human N-acetylome is unclear. In humans, the Huntingtin yeast partner K (HYPK) binds to the ribosome-associated Nα-acetyltransferase A (NatA) complex that acetylates ~40% of the proteome in humans and Arabidopsis thaliana.
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