Date of Award




Document Type


Degree Name

Doctor of Philosophy (PhD)


Department of Biomedical Sciences

Content Description

1 online resource (xvi, 228 pages) : illustrations (some color)

Dissertation/Thesis Chair

Steven Hanes

Committee Members

Vishnu Chaturvedi, Joan Curcio, Randall Morse, Patrick Van Roey, Joseph Wade


Candida albicans, morphogenetic switching, prolyl isomerase, RNA polymerase II, RNA sequencing, transcription, Antifungal agents, Peptidylprolyl isomerase

Subject Categories

Biology | Genetics | Molecular Biology


Candida albicans is a fungal pathogen that causes serious infections among immune-compromised patients and premature infants. C. albicans can become drug resistant, therefore, identifying new antifungal drug targets is an important goal. Here, we study a peptidyl-prolyl cis/trans isomerase called Ess1 as a potential drug target. Ess1 is conserved among pathogenic fungi, and therefore, potential inhibitors of Ess1 should display a broad spectrum of activity. We confirm that Ess1 is essential for growth in Candida albicans, but unlike the previously published find, deleting one copy of the C. albicans ESS1 gene did not affect morphogenetic switching. However, further reducing activity using a conditional mutant shows that Ess1 is important for this switch. An Ess1 ortholog called Pin1 is found in humans. Importantly, the structures of C. albicans Ess1 (CaEss1) and Pin1 show distinct features that suggest possible ways to selectively target the fungal enzyme. Toward this end, we generated mutations in a prominent alpha-helix that distinguishes CaEss1 from Pin1, but were unable to demonstrate functional consequences in vitro. It is possible that helix mutations will have affects in vivo using a mouse model. To further investigate functions of Ess1 in C. albicans, we undertook high-throughput RNA sequencing. Similar to results in S. cerevisiae, CaEss1 is required for efficient termination of small nucleolar RNA genes and repression of cryptic unstable transcripts, suggesting a conserved role. CaEss1 may also regulate genes important for host defense, oxidation-reduction, filamentous growth and biofilm formation. Our results support the goal of targeting CaEss1 for antifungal drug development, but reinforce the idea that inhibitors must distinguish fungal Ess1 from human Pin1.