Redox-driven regulation of UCHL3/Yuh1 influences mitochondrial health via the NEDD8/Rub1 pathway.

The ubiquitin-like protein NEDD8/Rub1 is initially translated as a precursor and undergoes maturation before becoming functional, a process mediated by the ubiquitin hydrolase UCHL3/Yuh1. Across studied organisms, the mature form of NEDD8/Rub1 modifies cullins, the central subunits of CRLs. NEDD8/Rub1 modification typically enhances CRL-mediated ubiquitination of key cellular regulators, leading to their proteasomal degradation. However, in S. cerevisiae, cullin modification by NEDD8/Rub1 occurs but does not regulate substrate turnover, prompting the question of whether NEDD8/Rub1 has a conserved role beyond CRL activation. Previous studies in S. cerevisiae have shown that increased production of reactive oxygen species (ROS) during the diauxic shift, a transition from glycolysis to mitochondrial respiration, inhibits cullin NEDDylation, though the specific enzymes affected remain unidentified. Here, we investigated how changes in the redox state affect Yuh1 catalytic function. Our findings reveal a thiol-based redox switch that modulates Yuh1 catalytic function in response to accumulated ROS. Our results suggest that the fine-tuning between the mature and precursor forms of NEDD8/Rub1 through temporal inactivation of Yuh1 is essential for maintaining mitochondrial integrity and enhancing resilience to oxidative stress. These results unveil a novel role for CRL-free NEDD8/Rub1 in redox signaling.