The scope of our ongoing research is to understand the mechanisms by which Candida albicans Hsp70 protein (Ssa1 and Saa2p) bind to and mediate uptake of salivary Histatin 5 (Hst 5), with the long-term goal of development of peptide-based alternative therapies for oral candidiasis. We found that although Ssa1p is more abundant than Ssa2p in C. albicans, it has a minimal role in Hst 5 binding, translocation and killing. Unexpected, we found Ssa1p is essential for oral and systemic virulence of this organism, and transcriptional analyses of ssa1 / cells identified 21 significantly down-regulated genes including cell wall adhesins such as PIR33. Since Hsp70 is known to bind both transcription factors and promoter region DNA in other yeast, we asked whether Candidal Ssa1p could regulate gene transcription though direct binding to promoter regions. Using EMSA analyses, we found that Ssa1p can specifically interact with PIR33 promoter GC rich DNA region, supporting its involvement in transcriptional regulation. These data point to an exciting new role for Ssa1p in C. albicans that involves regulation of gene expression by binding to transcriptional factors or DNA, or perhaps control of mRNA decay. We will investigate these possibilities by 1) identifying C. albicans genes regulated by Ssa1p using intergenic transcriptional profiling of Ssa1p with ChIP-Chip assays, and 2) determining whether Ssa1p can target RNA directly to control mRNA decay rates. These proposed experiments are outside the original aims of the Parent Grant DE10641project, therefore, this revision application requests funding for these studies in the remaining year of the parent project. We anticipate that data generated from this aim will accelerate the tempo of research by showing a novel role of ssa1p in transcriptional regulation of genes involved in the virulence of C. albicans, and allow for job creation by hiring an additional post-doctoral fellow to complete this aim.
As a part of the funded aims of our project, we found that Hst 5 uptake into the yeast cell and its killing ability requires primarily C. albicans Ssa2p, but that Ssa1p is required for fungal virulence in both systemic and oral thrush. Therefore, additional funding is requested to test whether Ssa1p can function as a DNA-binding transcriptional factor or co-activator of C. albicans genes by whole-genome transcriptional profiling of Ssa1p using ChIP-Chip assays, or if Ssa1p regulates gene expression by targeting RNA molecules directly to control mRNA decay rates in order to define a novel role of Ssa1p in transcriptional regulation of genes involved in the virulence of C. albicans. The proposed experiments will be accomplished during the final year of the parent grant and accelerate the tempo of our research by generating new data for additional publications and a new research project.
Showing the most recent 10 out of 47 publications
