N-terminal acetylation shields proteins from degradation and promotes age-dependent motility and longevity

Abstract

Most eukaryotic proteins are N-terminally acetylated, but the functional impact on a global scale has remained obscure. Using genome-wide CRISPR knockout screens in human cells, we reveal a strong genetic dependency between a major N-terminal acetyltransferase and specific ubiquitin ligases. Biochemical analyses uncover that both the ubiquitin ligase complex UBR4-KCMF1 and the acetyltransferase NatC recognize proteins bearing an unacetylated N-terminal methionine followed by a hydrophobic residue. NatC KO-induced protein degradation and phenotypes are reversed by UBR knockdown, demonstrating the central cellular role of this interplay. We reveal that loss of Drosophila NatC is associated with male sterility, reduced longevity, and age-dependent loss of motility due to developmental muscle defects. Remarkably, muscle-specific overexpression of UbcE2M, one of the proteins targeted for NatC KO-mediated degradation, suppresses defects of NatC deletion. In conclusion, NatC-mediated N-terminal acetylation acts as a protective mechanism against protein degradation, which is relevant for increased longevity and motility.

Biallelic NAA60 variants with impaired N-terminal acetylation capacity cause autosomal recessive primary familial brain calcifications

“…The functional impact of Nt-acetylation varies from protein to protein and may involve protein folding, degradation, stabilization, subcellular targeting, and protein complex formation 19 , 34 . Recent data strongly suggest that a major function of Nt-acetylation is shielding proteins from proteasomal degradation 38 – 40 . Interestingly, NatC Nt-acetylates a subset of proteins starting with Met (Met-Leu-, Met-Ile, Met-Phe, Met-Trp, Met-Val, Met-Met, Met-Lys etc.)…”

“…Interestingly, NatC Nt-acetylates a subset of proteins starting with Met (Met-Leu-, Met-Ile, Met-Phe, Met-Trp, Met-Val, Met-Met, Met-Lys etc.) 37 , 41 – 43 , and for many of these proteins, lack of NatC-mediated Nt-acetylation will cause them to be recognized by specific ubiquitin E3 ligases and degraded 38 in the N-degron pathway 44 . NatC and NatF have distinct in vivo substrates since NatC acts co-translationally on a variety of proteins while NatF acts post-translationally on transmembrane proteins, but these two enzymes acetylate similar types of protein N-terminal sequences 34 .…”

The logic of protein post‐translational modifications (PTMs): Chemistry, mechanisms and evolution of protein regulation through covalent attachments

“…[157] One particularly well-studied class of docking motifs are degrons, which target proteins for ubiquitylation by the combined action of E3 and E2 enzymes. [40] Degrons are often located on protein termini, [38,156,158,159] although they can be internal as well. The interaction of some degrons with ubiquitin E3 ligases is regulated by other PTMs such as phosphorylation or acetylation, which can either prevent or promote binding to the ligase, [158,160] providing an example of PTM…”

“…[40] Degrons are often located on protein termini, [38,156,158,159] although they can be internal as well. The interaction of some degrons with ubiquitin E3 ligases is regulated by other PTMs such as phosphorylation or acetylation, which can either prevent or promote binding to the ligase, [158,160] providing an example of PTM…”

N-terminal cysteine acetylation and oxidation patterns may define protein stability

“…and usually precedes other modifications 20 . One of the most common N-terminal modifications is acetylation, which can lead to a range of functional effects for the target protein, including stabilisation 21 – 23 . We therefore chose to focus on Nt-acetylation, which is catalysed by N-terminal acetyltransferases (NATs), with NatA being the enzyme presumed to be responsible for Nt-Cys acetylation (Fig.…”