Loss of Gst1 enhances resistance to MMS by reprogramming the transcription of DNA damage response genes in a Rad53-dependent manner in Candida albicans

The DNA damage response is a highly conserved protective mechanism that enables cells to cope with various lesions in the genome. Extensive studies across different eukaryotic cells have identified the crucial roles played by components required for response to DNA damage. When compared to the essential signal transducers and repair factors in the DNA damage response circuitry, the negative regulators and underlying mechanisms of this circuitry have been relatively under-examined. In this study, we investigated Gst1, a putative glutathione transferase in the fungal pathogen Candida albicans. We found that under stress caused by the DNA damage agent MMS, GST1 expression was significantly upregulated, and this upregulation was further enhanced by the loss of the checkpoint kinases and DNA repair factors. Somewhat counterintuitively, deletion of GST1 conferred increased resistance to MMS, potentially via enhancing the phosphorylation of Rad53. Furthermore, overexpression of RAD53 or deletion of GST1 resulted in upregulated transcription of DNA damage repair genes, including CAS1, RAD7, and RAD30, while repression of RAD7 transcription in the GST1 deletion reversed the strain's heightened resistance to MMS. Finally, Gst1 physically interacted with Rad53, and their interaction weakened in response to MMS-induced stress. Overall, our findings suggest a negative regulatory role for GST1 in DNA damage response in C. albicans, and position Gst1 within the Rad53-mediated signaling pathway. These findings hold significant implications for understanding the mechanisms underlying the DNA damage response in this fungal pathogen and supply new potential targets for therapeutic intervention.