scholarly journals The Not4 RING E3 Ligase: A Relevant Player in Cotranslational Quality Control

2013 ◽  
Vol 2013 ◽  
pp. 1-19 ◽  
Author(s):  
Martine A. Collart
Keyword(s):  
Quality Control ◽  
Ubiquitin Ligase ◽  
E3 Ligase ◽  
Rna Degradation ◽  
The Other ◽  
Ring E3 Ligase ◽  
Ideal Position ◽  
Evolutionarily Conserved ◽  
A Subunit ◽  
Ring E3

The Not4 RING E3 ligase is a subunit of the evolutionarily conserved Ccr4-Not complex. Originally identified in yeast by mutations that increase transcription, it was subsequently defined as an ubiquitin ligase. Substrates for this ligase were characterized in yeast and in metazoans. Interestingly, some substrates for this ligase are targeted for polyubiquitination and degradation, while others instead are stable monoubiquitinated proteins. The former are mostly involved in transcription, while the latter are a ribosomal protein and a ribosome-associated chaperone. Consistently, Not4 and all other subunits of the Ccr4-Not complex are present in translating ribosomes. An important function for Not4 in cotranslational quality control has emerged. In the absence of Not4, the total level of polysomes is reduced. In addition, translationally arrested polypeptides, aggregated proteins, and polyubiquitinated proteins accumulate. Its role in quality control is likely to be related on one hand to its importance for the functional assembly of the proteasome and on the other hand to its association with the RNA degradation machines. Not4 is in an ideal position to signal to degradation mRNAs whose translation has been aborted, and this defines Not4 as a key player in the quality control of newly synthesized proteins.

scholarly journals A glycine-specific N-degron pathway mediates the quality control of protein N-myristoylation

Science ◽  
2019 ◽  
Vol 365 (6448) ◽  
pp. eaaw4912 ◽  
Author(s):  
Richard T. Timms ◽  
Zhiqian Zhang ◽  
David Y. Rhee ◽  
J. Wade Harper ◽  
Itay Koren ◽  
...  
Keyword(s):  
Quality Control ◽  
Protein Stability ◽  
Protein Degradation ◽  
E3 Ligase ◽  
Cleavage Sites ◽  
Caspase Cleavage ◽  
E3 Ligases ◽  
Ring E3 Ligase ◽  
The Stability ◽  
Ring E3

The N-terminal residue influences protein stability through N-degron pathways. We used stability profiling of the human N-terminome to uncover multiple additional features of N-degron pathways. In addition to uncovering extended specificities of UBR E3 ligases, we characterized two related Cullin-RING E3 ligase complexes, Cul2ZYG11B and Cul2ZER1, that act redundantly to target N-terminal glycine. N-terminal glycine degrons are depleted at native N-termini but strongly enriched at caspase cleavage sites, suggesting roles for the substrate adaptors ZYG11B and ZER1 in protein degradation during apoptosis. Furthermore, ZYG11B and ZER1 were found to participate in the quality control of N-myristoylated proteins, in which N-terminal glycine degrons are conditionally exposed after a failure of N-myristoylation. Thus, an additional N-degron pathway specific for glycine regulates the stability of metazoan proteomes.

scholarly journals Overlapping function of Hrd1 and Ste24 in translocon quality control provides robust channel surveillance

2020 ◽  
Vol 295 (47) ◽  
pp. 16113-16120
Author(s):  
Avery M. Runnebohm ◽  
Kyle A. Richards ◽  
Courtney Broshar Irelan ◽  
Samantha M. Turk ◽  
Halie E. Vitali ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Quality Control ◽  
Endoplasmic Reticulum ◽  
Ubiquitin Ligase ◽  
Biological Membranes ◽  
The Other ◽  
Growth Defect ◽  
Zinc Metalloprotease

Translocation of proteins across biological membranes is essential for life. Proteins that clog the endoplasmic reticulum (ER) translocon prevent the movement of other proteins into the ER. Eukaryotes have multiple translocon quality control (TQC) mechanisms to detect and destroy proteins that persistently engage the translocon. TQC mechanisms have been defined using a limited panel of substrates that aberrantly occupy the channel. The extent of substrate overlap among TQC pathways is unknown. In this study, we found that two TQC enzymes, the ER-associated degradation ubiquitin ligase Hrd1 and zinc metalloprotease Ste24, promote degradation of characterized translocon-associated substrates of the other enzyme in Saccharomyces cerevisiae. Although both enzymes contribute to substrate turnover, our results suggest a prominent role for Hrd1 in TQC. Yeast lacking both Hrd1 and Ste24 exhibit a profound growth defect, consistent with overlapping function. Remarkably, two mutations that mildly perturb post-translational translocation and reduce the extent of aberrant translocon engagement by a model substrate diminish cellular dependence on TQC enzymes. Our data reveal previously unappreciated mechanistic complexity in TQC substrate detection and suggest that a robust translocon surveillance infrastructure maintains functional and efficient translocation machinery.

scholarly journals Structure and dynamics of the ASB9 CUL-RING E3 Ligase

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryan J. Lumpkin ◽  
Richard W. Baker ◽  
Andres E. Leschziner ◽  
Elizabeth A. Komives
Keyword(s):  
E3 Ligase ◽  
Structure And Dynamics ◽  
Ring E3 Ligase ◽  
Ring E3
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