Abf1 negatively regulates the expression of EPA1 and affects adhesion in Candida glabrata

. Adherence is a major virulence trait in that, in many strains, depends on the (epithelial adhesin) genes, which confer the ability to adhere to epithelial and endothelial cells of the host. The genes are generally found at subtelomeric regions, which makes them subject to subtelomeric silencing. In , subtelomeric silencing depends on different protein complexes, such as silent information regulator and yKu complexes, and other proteins, such as Repressor/activator protein 1 (Rap1) and Abf1. At the locus, which encodes the main adhesin Epa1, we previously found at least two -acting elements, the protosilencer Sil2126 and the negative element, that contribute to the propagation of silencing from the telomere to the subtelomeric region. . Abf1 binds to the regulatory regions of and other regions at the telomere E-R, thereby negatively regulating transcription. . To determine whether Abf1 and Rap1 silencing proteins bind to previously identified acting elements on the right telomere of chromosome E (E-R subtelomeric region), resulting in negative regulation of transcription and infer Abf1 and Rap1 recognition sites in . . We used chromatin immunoprecipitation (ChIP) followed by quantitative PCR to determine the binding sites for Abf1 and Rap1 in the intergenic regions between and and and , and mutants were used to determine the silencing level of the promoter region. . We found that Abf1 predominantly binds to the promoter region, leading to negative regulation of expression. Furthermore, the mutant , which lacks the last 43 amino acids at its C-terminal end and is defective for subtelomeric silencing, exhibits hyperadherence to epithelial cells compared to the parental strain, suggesting that is derepressed. We also determined the motif-binding sequences for Abf1 and Rap1 in using data from the ChIP assays. . Together these data indicate that Abf1 negatively regulates expression, leading to decreased adhesion of to epithelial cells.