The morphogenetic regulator Czf1p is a DNA-binding protein that regulates white opaque switching in Candida albicans.

Czf1p has been demonstrated to regulate the switch between the yeast-cell morphology and filamentous morphologies of the human fungal pathogen Candida albicans. The predicted amino acid sequence of Czf1p contains a zinc-cluster motif similar to the DNA-binding domains of proteins such as Saccharomyces cerevisiae Gal4p, suggesting that Czf1p is a DNA-binding protein. Czf1p also demonstrates genetic interaction and a two-hybrid interaction with a second regulator of C. albicans cellular morphology, Efg1p. During growth in contact with an agar matrix, Efg1p has a negative effect on filamentation and Czf1p antagonizes this effect. In addition to regulating cellular morphology, Efg1p plays a role in regulating the cell-type switch between the commonly observed white phase of C. albicans and the opaque, mating-competent phase. While overexpression of EFG1 stimulates the switch from opaque to white, the results reported here demonstrate that overexpression of CZF1 promotes the reverse switch, from white to opaque. We also demonstrate that Czf1p binds CZF1 promoter DNA in vitro. Therefore, for the regulation of both contact-dependent filamentation and white-opaque switching, Czf1p and Efg1p have opposing functions.