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Figure 1: N-terminal acetylation by NatC shields proteins from degradation. (Left) The NatC complex acetylates proteins harboring a hydrophobic residue in the second position (MΦ). Following Nt-acetylation, Ac-UBE2M and Ac-UBE2F promote cullin neddylation (N8), resulting in ubiquitylation (Ub) and proteasomal degradation of targeted cullin substrates, Ac-ARFRP1 is targeted to the Golgi where it plays a role in the secretory pathway, while the hypothetical proteins Ac-X and Ac-Y are thought to affect the secretory pathway and mitochondria, respectively. (Right) Loss of NatC exposes unacetylated MΦ-starting N-termini which serves as N-degrons that can be recognized by a set of N-recognins leading to proteasomal and, in some cases, lysosomal degradation. Non-Nt-acetylated NatC substrates are primarily targeted by the ubiquitin ligases UBR4-KCMF1 and to some extent UBR1 and UBR2. Targeted degradation of non-Nt-acetylated NatC substrates leads to decreased cullin neddylation, increased mitochondrial elongation and fragmentation, and is thought to affect intracellular trafficking. (Figure from Varland, Sylvia et al, 2023, Nature Communications)
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Arnesen Lab, UiB
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