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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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE221447 | GEO | 2023/09/18

REPOSITORIES: GEO

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Project description:The role of different proteins, Always Early (Aly), Spermatocyte Arrest (Sa), Ubi-p63E (Magn) on the gene expression in spermatocyte differentation was assessed by microarray ABSTRACT: The ubiquitin proteasome system (UPS) regulates many biological pathways by posttranslationally ubiquitinating proteins for degradation. Although maintaining a dynamic balance between free ubiquitin and ubiquitinated proteins is key to UPS function, the mechanisms that regulate ubiquitin homeostasis in different tissues through development are not clear. Here we show that loss of function of Drosophila magellan (magn), the polyubiquitin Ubi-p63E, results in specifically meiotic arrest sterility in males. Expression of ubiquitin from magn/Ubi-p63E contributes predominantly to maintaining the free ubiquitin pool in testes. Function of magn/Ubip63E is required cell autonomously for proper meiotic chromatin condensation, cell cycle progression and spermatid differentiation. magn/Ubi-p63E mutant germ cells develop normally to the spermatocyte stage but arrest at the G2/M transition of meiosis I with lack of protein expression of key meiotic cell cycle regulators Boule and Cyclin B. Loss of function of magn/Ubi-p63E did not strongly affect the spermatocyte transcription program regulated by the tTAF and tMAC genes. Knocking down proteasome function specifically in spermatocytes caused a different meiotic arrest phenotype, suggesting that the magn/Ubi-p63E phenotype may not result from general defects in protein degradation. Our results suggest a conserved role of polyubiquitin genes in male meiosis and a potential mechanism leading to meiosis I maturation arrest. RNA was obtained from whole testes of flies with following mutations: 1) aly[2]/aly[5p], 2) sa[1]/sa[2], 3) magn[12c]/magn[23b] or magn[12c]/magn[12c];pSC2, 4) red[1], e[1] (WT). Each genotype had three biological replicates except magn which had four total biological replicates, two from magn[12c]/[23b] and two from [12c]/[12c]; pSC2

Project description:In Arabidopsis thaliana the evolutionary conserved N-terminal acetyltransferase (Nat) complexes NatA and NatB co-translationally acetylate 60% of the proteome. Both have recently been implicated in the regulation of plant stress responses. While NatA mediates drought tolerance, NatB is required for pathogen resistance and the adaptation to high salinity and high osmolarity. Salt and osmotic stress impair protein folding and result in the accumulation of misfolded proteins in the endoplasmic reticulum (ER). The ER-membrane resident E3 ubiquitin ligase DOA10 targets misfolded proteins for degradation during ER stress and is conserved among eukaryotes. In yeast, DOA10 recognizes conditional degradation signals (Ac/N-degrons) created by NatA and NatB. Assuming that this mechanism is preserved in plants, the lack of Ac/N-degrons required for efficient removal of misfolded proteins might explain the sensitivity of NatB mutants to protein harming conditions. In this study, we investigate the response of NatB mutants to dithiothreitol (DTT) and tunicamycin (TM) induced ER stress. We report that NatB mutants are hypersensitive to DTT but not TM, suggesting that the DTT hypersensitivity is caused by an over-reduction of the cytosol rather than an accumulation of unfolded proteins in the ER. In line with this hypothesis, the cytosol of NatB depleted plants is constitutively over-reduced and a global transcriptome analysis reveals that their reductive stress response is permanently activated. Moreover, we demonstrate that doa10 mutants are susceptible to neither DTT nor TM, ruling out a substantial role of DOA10 in ER-associated protein degradation (ERAD) in plants. Contrary to previous findings in yeast, our data indicates that N-terminal acetylation (NTA) does not inhibit ER targeting of a substantial amount of proteins in plants. In summary, we provide further evidence that NatB-mediated imprinting of the proteome is vital for the response to protein-harming stress and rule out DOA10 as the sole recognin for substrates in the plant ERAD pathway.

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

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