Lysine acetylation is one of the most prominent post-translational modifications (PTM) of proteins and has been recognized to play a key role in regulation of gene expression by histone modification and modulation of chromatin function. Despite impressive advances in our understanding of lysine acetyltransferases (KATs) and lysine deacetylases (KDACs) during the last decades, the role of reversible lysine acetylation in fundamental cellular processes in physiology and pathology from cancer to infectious diseases still remains poorly understood. In particular, the dissection of chromatin and non-chromatin functions of individual KATs/KDACs members still represents a major scientific challenge. For example, there is compelling evidence that lysine acetylation of proteins modulates virulence of pathogenic fungi such as Candida albicans, but the underlying mechanisms have remained largely unexplored. Understanding these mechanisms is all the more important because the recognition motifs of C. albicans acetyltransferases KATs are unique to the fungal kingdom and thus represent promising targets for antifungal drug discovery. The central hypothesis of the proposed research is that protein acetylation plays pivotal roles in controlling the cellular physiology and virulence of C. albicans. We formulated this hypothesis based on our preliminary data indicating that lysine acetylation is an abundant form of PTM in C. albicans. Furthermore, our previous work has implicated C. albicans Hat1, a paradigmatic histone lysine acetylase, in DNA damage repair, morphogenesis, biofilm formation, antifungal drug resistance, and virulence. However, the roles of several other lysine acetyltransferase enzymes in this organism have remained unknown. Our preliminary studies have also implicated acetylation at two specific lysine residues (K654 and K655) of Lig4, an important protein involved in Non-Homologous End Joining (NHEJ)-dependent DNA repair and modulating morphogenesis and virulence of C. albicans. Furthermore, new preliminary RNA-seq data suggest that Hat1 has important roles in mitochondrial function, as well as in the processing and regulation of non-coding RNAs (ncRNA). The main objective in our joint application is therefore to identify and characterize the histone and non-histone target genes of C. albicans Hat1 and to investigate its ill-defined role in regulation of mitochondrial function and a possible role in the NHEJ DNA repair. Guided by the preliminary data, we expect to test our central hypothesis and to accomplish the objectives of this application by pursuing the following three Specific Aims: 1) To identify and characterize both histone and non- histone (non-chromatin) targets of Hat1. 2) To investigate the possible role of acetylation of the NHEJ DNA repair pathway in regulation of C. albicans virulence. 3) To investigate role of Hat1 in the processing of ncRNA. The payoffs of this proposal are expected to be significant because we expect to uncover novel modes of regulation of key cellular processes important for pathogenesis of C. albicans.
The proposed research is relevant to public health because the identification and characterization of Hat1 acetylome will highly likely uncover novel modes of regulation of key cellular processes important for pathogenesis of C. albicans in addition to fundamentally advancing the field of Candida and candidiasis. Thus the proposed research is relevant to the part of NIH's mission that pertains to developing fundamental knowledge that will help reduce the burdens of human disease.
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