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Orphan quality control by an SCF ubiquitin ligase directed to pervasive C-degrons

ABSTRACT: Selective protein degradation typically involves substrate recognition via short linear motifs known as degrons. Various degrons can be found at protein termini from bacteria to mammals. While N-degrons have been extensively studied, our understanding of C-degrons is still limited. Towards a comprehensive understanding of eukaryotic C-degron pathways, we performed an unbiased survey of C-degrons in budding yeast. We identified over 5000 potential C-degrons by stability profiling of random peptide libraries and of the yeast C-terminome. Combining machine learning, high-throughput mutagenesis and genetic screens revealed that the SCF ubiquitin ligase targets ~40% of degrons using a single F-box substrate receptor Das1. Although sequence-specific, Das1 is highly promiscuous, recognizing a variety of C-degron motifs. By screening for full-length substrates, we implicate SCFDas1 in degradation of orphan protein complex subunits. Altogether, this work highlights the variety of C-degron pathways in eukaryotes and uncovers how an SCF/C-degron pathway of broad specificity contributes to proteostasis.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE246422 | GEO | 2023/11/01

REPOSITORIES: GEO

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Project description:N-degron pathway plays an important role in the protein quality control and maintenance of cellular protein homeostasis. ZER1 and ZYG11B, the substrate receptors of the Cullin 2-RING E3 ubiquitin ligase (CRL2), recognize N-terminal (Nt) glycine degrons and participate in the Nt-myristoylation quality control through the Gly/N-degron pathway. Here we show that ZER1 and ZYG11B can also recognize small Nt-residues other than glycine. Specifically, ZER1 preferentially binds to Nt-serine, -alanine, -threonine and -cysteine over -glycine, while ZYG11B prefers Nt-glycine but also has the capacity to recognize Nt-serine, -alanine and -cysteine in vitro. Nt-serine, -alanine and -cysteine undergo Nt-acetylation by NatA, thereby shielding them from recognition by ZER1/ZYG11B in cells. We found that ZER1/ZYG11B is able to target the non-acetylation of small Nt-residue degrons for degradation in NatA-deficient cells, implicating its role in the Nt-acetylation quality control. Furthermore, we present the crystal structures of ZER1 and ZYG11B bound to various small Nt-residues and uncover the molecular mechanism of non-acetylated substrate recognition by ZER1 and ZYG11B.N-degron pathway plays an important role in the protein quality control and maintenance of cellular protein homeostasis. ZER1 and ZYG11B, the substrate receptors of the Cullin 2-RING E3 ubiquitin ligase (CRL2), recognize N-terminal (Nt) glycine degrons and participate in the Nt-myristoylation quality control through the Gly/N-degron pathway. Here we show that ZER1 and ZYG11B can also recognize small Nt-residues other than glycine. Specifically, ZER1 preferentially binds to Nt-serine, -alanine, -threonine and -cysteine over -glycine, while ZYG11B prefers Nt-glycine but also has the capacity to recognize Nt-serine, -alanine and -cysteine in vitro. Nt-serine, -alanine and -cysteine undergo Nt-acetylation by NatA, thereby shielding them from recognition by ZER1/ZYG11B in cells. We found that ZER1/ZYG11B is able to target the non-acetylation of small Nt-residue degrons for degradation in NatA-deficient cells, implicating its role in the Nt-acetylation quality control. Furthermore, we present the crystal structures of ZER1 and ZYG11B bound to various small Nt-residues and uncover the molecular mechanism of non-acetylated substrate recognition by ZER1 and ZYG11B.

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Orphan quality control by an SCF ubiquitin ligase directed to pervasive C-degrons

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