白色念珠菌組蛋白 H3 第四離胺酸去甲基酶 Jhd2 的功能探討

Abstract

Candida albicans is an opportunistic human fungal pathogen. Invading and damaging host tissues when the equilibrium of individual environment is disturbed. Nosocomial infection prolong the discharge time of patients, which increase personal and economic cost. The harmful side effect to human cell and resistance to antifungal drugs have made continuous development of new antifungal drugs necessary. Recent progress in developing small molecules to fungal cellular targets suggests that comprehensive understanding the molecular mechanism underlying Candida albicans virulence is essential to continunous exploration of drugs specific to cellular targets of Candida albicans. The transition of C. albicans among diverse morphological states and ability to form biofilm are the key determinants of its ability to cause systemic candidiasis and resistance to antifungal drugs. The biofilm structure prevents cells from being washed away and support the spread of cells. C. albicans exploits their capacity to adhere to many surfaces. However, it is remain incompletely understood as to how the environment cues are intertwined with genetic factors determines the alteration of adhesion properties. Our previous study reveals that CaCdc4, functioning through the E3 ubiquitin ligase, participates in the repression in filamentous growth of C. albicans. We have identified CaORF19.5651(CaJHD2) as one of the CaCdc4 associated proteins by affinity purification. Jhd2 is histone H3 lysine 4 (H3K4) demethylase in Saccharomyces cerevisiae and other species. CaJhd2 possesses a highly conserved JmjC domain-containg demetylase 2 that is known to require for demethylation of H3K4. It is known that the H3K4 methylation contribute to the capacity of adhesion and morphogenesis in C. albicans. As a result, I aim to investigate the H3K4 demethylase activity of CaJhd2 and the functional consequence of CaJHD2 deficiency. The demethylase of H3K4 of C. albicans has not been verified to date, and the H3K4 methylated modification remains poorly known. To investigate whether the CaJhd2 is a demethylase specifically for H3K4, I constructed a homozygous jhd2 null mutant jhd2Δ/Δ using wild-type strain SC5314 and have examined the mono-, di-, and trimethylation levels of H3K4 of the mutant in comparison with those of the wild-type strain. I confirmed that the CaJhd2 is a H3K4 mono-demethylase of C. albicans but the di-, tri- demethylase activity specifically for H3K4 remains undetermined. In addition, I observed increase of cellular flocculation of jhd2Δ/Δ in relation in spider medium that contains mannitol and phosphate. This suggests that the deficiency of CaJHD2 may be involved in adhesion of cell-to-cell and cell to nonbiotic materials, although its effect to the ability of biofilm formation in C. albicans remains inconclusive.