Yeast N^α‐terminal acetyltransferases are associated with ribosomes

Abstract

N-terminal acetylation is one of the most common modifications, occurring on the vast majority of eukaryotic proteins. Saccharomyces cerevisiae contains three major NATs, designated NatA, NatB, and NatC, with each having catalytic subunits Ard1p, Nat3p, and Mak3p, respectively. Gautschi et al. (Gautschi et al. [2003] Mol Cell Biol 23: 7403) previously demonstrated with peptide crosslinking experiments that NatA is bound to ribosomes. In our studies, biochemical fractionation in linear sucrose density gradients revealed that all of the NATs are associated with mono- and polyribosome fractions. However only a minor portion of Nat3p colocalized with the polyribosomes. Disruption of the polyribosomes did not cause dissociation of the NATs from ribosomal subparticles. The NAT auxiliary subunits, Nat1p and Mdm20p, apparently are required for efficient binding of the corresponding catalytic subunits to the ribosomes. Deletions of the genes corresponding to auxiliary subunits significantly diminish the protein levels of the catalytic subunits, especially Nat3p, while deletions of the catalytic subunits produced less effect on the stability of Nat1p and Mdm20p. Also two ribosomal proteins, Rpl25p and Rpl35p, were identified in a TAP-affinity purified NatA sample. Moreover, Ard1p copurifies with Rpl35p-TAP. We suggest that these two ribosomal proteins, which are in close proximity to the ribosomal exit tunnel, may play a role in NatA attachment to the ribosome.

N-terminal acetylome analyses and functional insights of the N-terminal acetyltransferase NatB

“…In contrast, our phenotype and proteomics data presented here demonstrated only a partial rescue of yNatB function by heterologously expressed hNatB, and may hint to the fact that, given the observed general decrease in the overall levels of Nt-acetylation of NatB substrates, the Nt-acetylation levels of a (few) specific NatB substrates get critically low for their proper activity, explaining the observed phenotypic differences between the control and y[hNatB] strains and in-line with previous comparative phenotypic substrate analysis (18). The not fully effective functioning of hNatB in yeast might be caused by an altered assemblage or association with yeast ribosomes (41), (subtle) differences in substrate specificities, or the additional requirement of cofactors and posttranslational protein modifications. In fact, the observed partial Nt-acetylation of NatB substrates by hNatB in yeast is in-line with the Nt-acetylation effects observed upon knocking down NatB in HeLa cells.…”

Tubedown associates with cortactin and controls permeability of retinal endothelial cells to albumin

“…In agreement with this hypothesis, the yeast NatA complex has been shown to be involved in ribosome biogenesis (Gautschi et al, 2003;Polevoda et al, 2008). In addition, Tbdn colocalizes with the Factin cytoskeleton in the cytoplasm.…”

Expression of humanNAA11(ARD1B) gene is tissue-specific and is regulated by DNA methylation

“…NatA is composed of a catalytic subunit called Naa10p (also known as ARREST DEFECTIVE 1A; ARD1A) and an auxiliary subunit called Naa15p (also known as NMDA-receptor regulated 1; NARG1; NATH; NAT1) that is responsible for docking the NatA to ribosomes. 4,5 Formation of ARD1A-NARG1 heterodimer is required for NAT activity. 6 NAA10 gene encodes the catalytic subunit of N(alpha)-acetyltransferase NatA that catalyzes the acetylation of the N-termini of many eukaryotic proteins.…”