DNA Repair Mechanisms in Candida albicans

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EXCEED THE SPACE PROVIDED. DNA repair in the human pathogen Candida albicans has not been studied to any great extent in spite of numerous observations that suggest extensive genomic variability among isolates. It is likely that this variability is a reflection of a variety of genomic alterations that include, deletions, translocations, ploidy changes, as well as loss of chromosomes or parts of chromosomes. The consequence of several of these processes has not been determined, but aneuploidy in this organism has been associated with the utilization of a carbohydrate as well as drug resistance. Homologous recombination [HR] and non-homologous end- joining [NHEJ] should be important components in DNA repair as a consequence of these genomic alterations. Beyond the role of these pathways in DNA repair, we have shown that strains of C. albicans deleted of LIG4 [NHEJ pathway] or RAD52 [HR pathway] have different growth phenotypes in that the lig 4 mutant is unable to form hyphae while the rad52 mutant forms filaments constitutively [i.e., even under non- inducing conditions]. These two observations indicate that DNA repair either directly or indirectly provides important functions in the morphogenesis of this organism. To understand the roles of these two DNA repair pathways in this organism, we propose four specific aims. Specific aim 1 includes the construction of new mutants in each of these two pathways. Lig4 and rad52 mutants have been constructed but others are needed to identify gene functions. In specific aim 2, proteins that interact with Lig4p will be identified. It is clear from the literature that the interacting proteins are different from those described for the Lig4p of S. cerevisiae. Microarray analysis will also be used to identify genes whose expression is regulated by Lig4p Specific aim 3 focuses upon the role of the HR and NHEJ proteins in DNA repair and morphogenesis, while specific aim 4 explores the relationship of candidate genes with virulence. In this regard, we have already published data that indicates a role for Lig4p in the virulence of C. albicans in an invasive model of candidiasis. We will now test this same mutant as well as the rad52 mutant in oral and vaginal candidiasis. The outcome of these studies will not only be the identification of proteins whose functions include DNA repair but also their role in morphogenesis. It is rather easy to believe that this unconventional human pathogen utilizes single pathways for multiple functions. PERFORMANCE SITE ========================================Section End===========================================