Exploring the role of the CCAAT-binding complex in cell wall maintenance and biofilm formation in Candida albicans

The conserved CCAAT-binding complex (CBC) specifically recognizes and binds to the CCAAT motif present in eukaryotic promoters, thereby controlling gene transcription. In Candida albicans, the CBC cooperates with another transcription factor, Hap43, to regulate iron homeostasis. Moreover, several Hap43-independent functions have also been uncovered. However, the functions of CBC have not been extensively characterized.

Deletion mutants lacking each component of the CBC were independently compared to the wild-type strain with regard to cell wall properties, composition, and structure. The effects of CBC deletion on biofilm formation were also investigated. Finally, RNA-seq analysis was performed to reveal functional divergence between the two Hap3 paralogs, Hap31 and Hap32.

CBC deletion significantly impacts cell wall properties, composition, exposure of glucan and chitin, as well as cell wall remodeling. These effects appear to be associated with the small GTPase Rhb1 and the Mkc1 signaling pathway. Moreover, we showed that CBC deletion affects biofilm formation, which appears to be independent of Rhb1. RNA-seq analysis further revealed the broad roles of the Hap3 paralogs within the CBC.

Notably, this work provides new insights into the relationship among CBC, cell wall maintenance, and biofilm formation in C. albicans.