闡述光滑念珠菌SAGA複合體中Dub模組的功能

Abstract

念珠菌菌血症(Candidiasis)為重要的真菌性疾病之一，泛指皮膚或黏膜組織等由念珠菌屬引起的疾病。光滑念珠菌(Candida glabrata)為伺機性病源，可附著於黏膜組織並侵入血管造成系統性感染，加上先天性耐藥性導致由原光滑念珠菌引起的感染逐漸增加。轉譯後修飾在表徵遺傳中有重要的功能，SAGA複合體調控兩種不同的轉譯後修飾包含將組蛋白乙醯化的HAT模組及去泛素化的Dub模組，其在基因調控上具決定性的作用，且在許多生物上具有高度的保守性。SAGA複合體在轉譯中具有co-activator的作用，可以依據功能分成不同的模組，其可以調控啤酒酵母菌約10%的基因表現，其中包含透過調控轉譯後修飾調控逆境相關的基因。實驗室先前研究發現SAGA複合體HAT模組中ADA2基因會調控光滑念珠菌對氧化壓力及藥物的耐受性、細胞壁的完整性和毒力，但SAGA複合體中其它模組在光滑念珠菌的作用尚未了解。本研究主要探討SAGA複合體中Dub模組基因(UBP8、SGF11、SGF73和SUS1)的功能，並發現Dub模組中會調控H2B去泛素化的基因(UBP8、SGF11、和SUS1)對於藥物耐受性、細胞壁完整性和生物膜的形成有重要的作用。另外，SGF73會影響對氧化壓力、藥物的耐受性、細胞壁完整性和生物膜形成。在小鼠系統性感染實驗中ubp8、sgf11和sus1突變株接近低毒力，而sgf73突變株並不會影響其毒力。總結，光滑念珠菌Dub模組在H2B去泛素化、細胞壁完整性、藥物耐受性及生物膜形成中扮演重要的角色。

Candidiasis is one of the most important fungal diseases and generally refers to diseases caused by Candida species in skin or mucosal tissues. Candida glabrata is an opportunistic human fungal pathogen and due to the innate antifungal drug tolerance and the ability to adhere to mucocutaneous surface of C. glabrata, the infections caused by C. glabrata have significantly increased. SAGA complex contains two different post-translational modifications including histone acetylation (HAT module) and deubiquitination (Dub module), which are decisive in gene regulation and highly conserved in eukaryotes. Previous research in our laboratory found that the HAT module ADA2 could regulate C. glabrata oxidative stress tolerance, drug tolerance, cell wall integrity and virulence. The roles of Dub module comprised of UBP8, SGF73, SGF11 and SUS1 genes in SAGA complex are not yet understood. We found that Dub module genes UBP8, SGF11 and SUS1 are involved in H2B deubiquitination. Furthermore, ubp8, sgf11 and sus1 mutants with increased H2B ubiquitination level exhibit decreased biofilm formation and sensitive to cell wall perturbing agent SDS and antifungal drug amphotericin B. Besides, sgf73 mutant was susceptible to oxidative stresses, antifungal drugs and cell wall perturbing agents. The ubp8, sgf11 and sus1 that involved in H2B deubiquitination showed marginal hypovirulence, while sgf73 mutant exhibited virulence similar to wild type in murine systemic infection model. In conclusion, C. glabrata Dub module plays critical roles in H2B deubiquitination, cell wall integrity, biofilm formation and drug tolerance and plays minor roles in virulence.