Wss1 and Ddi1 DNA-Protein crosslink repair proteases protect Saccharomyces cerevisiae and Candida albicans against oxidative stress.

Oxidative stress is a major microbicidal mechanism of phagocytes causing molecular damages, including DNA-protein crosslinks (DPCs), toxic DNA lesions that can lead to genomic instability. DPC repair depends on Wss1 and Ddi1 proteases, so they may be critical for fungal survival in hosts, yet their roles have not been fully elucidated. In this study, the roles of Wss1 and Ddi1 under oxidative stress were examined in the model yeast Saccharomyces cerevisiae and Candida albicans, an important human fungal pathogen. Direct measurements of DPCs using SDS/KCl precipitation showed that oxidative stress inducers, including hydrogen peroxide, sodium hypochlorite, menadione and plumbagin, increased DPC levels in a dose-dependent manner in both species. S. cerevisiae and C. albicans lacking Wss1 and Ddi1 are hypersensitive to oxidative stress inducers. Complementation assays demonstrated that catalytic activity of CaWss1 is essential, while the interactions with Cdc48 and SUMO are important but not absolutely required. Importantly, CaWss1 and CaDdi1 play partially redundant roles for resistance to macrophage killing, with CaWss1 being more dominant. In conclusion, Wss1 and Ddi1 in both S. cerevisiae and C. albicans are required for survival under oxidative stress, and this may be critical for C. albicans to evade phagocytic killing and establish an infection.