Adherence, an important virulence factor, is mediated by the (Epithelial Adhesin) genes in the opportunistic pathogen Expression of adhesin-encoding genes requires tight regulation to respond to harsh environmental conditions within the host. The majority of genes are localized in subtelomeric regions regulated by subtelomeric silencing, which depends mainly on Rap1 and the Sir proteins. adhesion to epithelial cells is primarily mediated by Epa1. forms a cluster with and in the right telomere of chromosome E (E). This telomere contains a -acting regulatory element, the protosilencer Sil2126 between and the telomere. Interestingly, Sil2126 is only active in the context of its native telomere. Replacement of the intergenic regions between genes in E revealed that -acting elements between and are required for Sil2126 activity when placed 32 kb away from the telomere (Sil@-32kb). Sil2126 contains several putative binding sites for Rap1 and Abf1, and its activity depends on these proteins. Indeed, Sil2126 binds Rap1 and Abf1 at its native position and also when inserted at -32 kb, a silencing-free environment in the parental strain. In addition, we found that Sil@-32kb and Sil2126 at its native position can physically interact with the intergenic regions between and respectively, by chromosome conformation capture assays. We speculate that Rap1 and Abf1 bound to Sil2126 can recruit the Silent Information Regulator complex, and together mediate silencing in this region, probably through the formation of a chromatin loop.

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Accurate DNA replication and segregation is key to reproduction and cell viability in all organisms. Autonomously replicating sequence-binding factor 1 (Abf1) is a multifunctional protein that has essential roles in replication, transcription, and regional silencing in the model yeast Saccharomyces cerevisiae. In the opportunistic pathogenic fungus Candida glabrata, which is closely related to S. cerevisiae, these processes are important for survival within the host, for example, the regulation of transcription of virulence-related genes like those involved in adherence. Here, we describe that CgABF1 is an essential gene required for cell viability and silencing near the telomeres, where many adhesin-encoding genes reside. CgAbf1 mediated subtelomeric silencing depends on the 43 C-terminal amino acids. We also found that abnormal expression, depletion, or overexpression of Abf1, results in defects in nuclear morphology, nuclear segregation, and transit through the cell cycle. In the absence of ABF1, cells are arrested in G2 but start cycling again after 9 h, coinciding with the loss of cell viability and the appearance of cells with higher DNA content. Overexpression of CgABF1 causes defects in nuclear segregation and cell cycle progression. We suggest that these effects could be due to the deregulation of DNA replication.