Histone acetyltransferase Gcn5-mediated histone H3 acetylation facilitates cryptococcal morphogenesis and sexual reproduction

Abstract

ABSTRACT Sexual reproduction is the primary driving force behind eukaryotic environmental adaptation and evolution. In the human fungal pathogen Cryptococcus neoformans , sexual reproduction plays a critical role in the emergence of highly virulent strains and drug-resistant variants. The sexual life cycle of C. neoformans commences with the yeast-hyphae transition in response to mating stimulation, followed by hyphal extension and further differentiation into basidium, where meiosis takes place to produce basidiospore. Although extensive studies have been conducted on the determining factors and genetic pathways involved in the sexual cycle, the precise contribution of epigenetic modifications in this process remains elusive. Here, through a systematic genetic screening assay, we find that Gcn5 is the specific histone acetyltransferase involved in yeast-hyphae morphogenesis in C. neoformans . Furthermore, we demonstrate that Gcn5 is indispensable for completing the entire sexual cycle of C. neoformans , including yeast-hyphae transition, hyphal development, basidium differentiation, meiosis, and subsequent sporulation. Additionally, chromatin immunoprecipitation assay demonstrates that Gcn5-mediated H3K14ac modification is closely associated with the activated transcription of master transcriptional regulator gene ZNF2 and its downstream targets under mating-inducing condition. Moreover, disruption of two additional subunits encoding gene within the SAGA complex, ADA3 and SPT20 , resulted in a similar phenotype to that observed with GCN5 deletion, indicating that Gcn5 functions in the context of an intact SAGA/ADA complex in regulating the sexual life cycle. Taken together, these results elucidated a key epigenetic modification, Gcn5-mediated histone acetylation, in orchestrating yeast-hyphae morphogenesis and sexual reproduction in the human fungal pathogen C. neoformans . IMPORTANCE Eukaryotic gene transcription is typically regulated by a series of histone modifications, which play a crucial role in adapting to complex environmental stresses. In the ubiquitous human fungal pathogen Cryptococcus neoformans , sexual life cycle is a continuous intracellular differentiation process that strictly occurs in response to mating stimulation. Despite the comprehensive identification of the regulatory factors and genetic pathways involved in its sexual cycle, understanding of the epigenetic modifications involved in this process remains quite limited. In this research, we found that histone acetyltransferase Gcn5-mediated histone H3 acetylation plays a crucial role in completing the cryptococcal sexual cycle, including yeast-hyphae morphogenesis and the subsequent sexual reproduction. Furthermore, we demonstrated that Gcn5 participates in this process primarily through regulating the key morphogenesis regulator Znf2 and its targets. This study thus provided a comprehensive understanding of how histone acetylation modification impacts sexual life cycle in a high-risk human pathogenic fungus.