Biology subjects

Bernardini, J. P.

Publications and source records attributed to Bernardini, J. P..

3 recordsLinked to original sources

bioRxiv2026

BAG6 and RNF126 promote the degradation of cytosolic misfolded proteins that contain buried degron motifs

Missense mutations account for the majority of catalogued human disease-associated variants, and many are predicted to destabilize proteins and promote their degradation. To characterize the pathways responsible for recognizing and clearing such variants, we employed a two-pronged approach to identify both quality control components mediating turnover of misfolded proteins and the sequence elements within their substrates that drive this process. Using a panel of unstable cytosolic missense variants in proximity-labeling and RNAi-based experiments, we identified the BAG6-RNF126 pathway as contributing to the clearance of a subset of these substrates. Applying a tile-based approach to a model cytosolic protein, we uncovered strong potential degrons, including a C-terminal degron degraded in part in a BAG6- and RNF126-dependent manner. Modeling supports that this degron can be accommodated by BAG6. Together, our findings add to the growing body of evidence implicating the BAG6-RNF126 pathway as a key mediator of cytosolic protein quality control.

molecular biology↗

bioRxiv2024

The co-chaperone DNAJA2 buffers proteasomal degradation of cytosolic proteins with missense mutations

Mutations can result in the loss of a proteins native function due to protein misfolding, which is generally handled by an intricate protein quality control network. To better understand the triaging mechanisms of misfolded cytosolic proteins, we screened a human mutation library to identify a panel of unstable mutations. The degradation of these mutated cytosolic proteins is largely dependent on the ubiquitin proteasome system. Using BioID proximity labelling, we found that the co-chaperones DNAJA1 and DNAJA2 are key interactors of one of the mutated proteins. Notably, the absence of DNAJA2 increases the turnover of the mutant protein but not of the wild-type protein. Our work indicates that missense mutations in cytosolic proteins can promote interactions with molecular chaperones that normally do not occur. Assessment of the broader panel of cytosolic mutant proteins shows that the co-chaperone DNAJA2 exhibits three distinct behaviours: acting to stabilize solely the mutant, both the wild-type and mutant proteins, or being dispensable. Our work illustrates how distinct elements of the protein homeostasis network are utilized in the presence of a cytosolic misfolded protein. Summary StatementWe identified a panel of cytosolic mutant proteins degraded by the proteasome. DNAJA2 is often required to prevent mutant protein turnover, even if it is sometimes dispensable for the wild-type protein.

cell biology↗

bioRxiv2020

Mechanism and inhibition of SARS-CoV-2 PLpro

Coronaviruses, including SARS-CoV-2, encode multifunctional proteases that are essential for viral replication and evasion of host innate immune mechanisms. The papain-like protease PLpro cleaves the viral polyprotein, and reverses inflammatory ubiquitin and anti-viral ubiquitin-like ISG15 protein modifications1,2. Drugs that target SARS-CoV-2 PLpro (hereafter, SARS2 PLpro) may hence be effective as treatments or prophylaxis for COVID-19, reducing viral load and reinstating innate immune responses3. We here characterise SARS2 PLpro in molecular and biochemical detail. SARS2 PLpro cleaves Lys48-linked polyubiquitin and ISG15 modifications with high activity. Structures of PLpro bound to ubiquitin and ISG15 reveal that the S1 ubiquitin binding site is responsible for high ISG15 activity, while the S2 binding site provides Lys48 chain specificity and cleavage efficiency. We further exploit two strategies to target PLpro. A repurposing approach, screening 3727 unique approved drugs and clinical compounds against SARS2 PLpro, identified no compounds that inhibited PLpro consistently or that could be validated in counterscreens. More promisingly, non-covalent small molecule SARS PLpro inhibitors were able to inhibit SARS2 PLpro with high potency and excellent antiviral activity in SARS-CoV-2 infection models.

biochemistry↗