Transcriptional condensates regulating Candida albicans pathogenesis

Project Summary/Abstract Candida albicans poses a critical threat as it is a leading cause of hospital-acquired fungal infections and is associated with increasing levels of antifungal resistance. As an opportunistic pathogen, C. albicans can colonize multiple parts of the human body and can cause infections like oropharyngeal candidiasis (OPC). Biofilms can form at mucosal infection sites, providing resistance to antifungals and the immune system, and can disseminate to cause systemic disease with mortality rates around 40%. Better understanding of C. albicans biofilm formation is therefore essential to understanding disease and for developing improved therapeutic strategies against this prevalent human pathogen. C. albicans biofilm formation is regulated by a regulatory network consisting of nine transcription factors (TFs). These TFs bind to their own promoters as well as that of the other TFs in the network and are likely recruited to the DNA, at least in part, via protein-protein interactions. Recent work in the Bennett laboratory revealed that seven of the nine core biofilm TFs contain prion-like domains (PLDs) that have been linked to phase separation (PS), a process in which a homogeneous solution demixes into a dense phase that is in equilibrium with a more dilute surrounding phase. Moreover, our group has directly shown that C. albicans PLD- containing TFs can undergo PS and linked this capacity to their ability to activate a phenotypic transition. Preliminary work reveals that several TFs critical to filamentation, biofilm formation, and virulence, can readily undergo PS and links this capacity to their function in C. albicans. Additional pilot experiments indicate that increasing the “valency” of a biofilm TF (its propensity to undergo protein-protein interactions) can increase PS and thereby increase functional activity. These studies establish that there is a critical need to understand PS in fungal TFs and its impact on gene expression and pathogenesis. I hypothesize that core biofilm TFs rely on their phase-separating capacity to function and that altering the valency of TFs will alter both their phase separation capacity and their role in gene expression. In Aim 1, I will characterize the phase-separating capacity and function of Efg1, a key biofilm network TF. In Aim 2, I will determine how changes in TF valency alter the formation of phase-separated condensates and thereby impact their function. Results from these experiments will reveal how biofilm TFs regulate transcription and will lead to novel therapeutic strategies against C. albicans. Furthermore, this fellowship aims to advance skills critical to a research career including scientific investigation, mentoring, and oral and written communication. Meetings with my sponsor and thesis committee, training of other lab members, writing of manuscripts, and presenting my work at conferences will improve such skills. The research plan will be conducted in the esteemed Bennett laboratory and the Pathobiology Graduate Program at Brown University, environments highly conducive to growth as an effective scientific investigator. Completing these aims will prepare me for a successful research career.