Epigenetic control of virulence in a fungal meningitis pathogen

 描述（由申请人提供）：我们在真菌脑膜炎病原体新型隐球菌中发现了多梳抑制复合物PRC 2，其通过赖氨酸27（H3K27me）上组蛋白H3的甲基化使染色质结构域沉默。这是第一个在人类病原体中发现的Polycomb系统。我们建议定义该系统的核心特性和组成部分，并研究H3K27me调节在适应宿主中的作用。动物和植物的Polycomb沉默系统是发育的重要表观遗传调节因子，显著地介导先前发育和环境事件的可遗传记忆。Polycomb系统由催化H3K27me的PRC2复合物和使H2A单偶联并介导染色质致密化的PRC1复合物组成。这种染色质也被称为兼性异染色质，因为它可以动态调节。据报道，少数其他真菌的基因组也编码预测的PRC2组分，这提高了该系统在该王国中作为一般表观遗传调节剂发挥作用的可能性。我们纯化了C.结果表明，它介导亚端粒H3K27三甲基化（H3K27me3）和染色体末端附近的基因沉默。我们的研究还表明，PRC2复合物的chromodomain亚基直接识别甲基转移酶的H3K27me3产物，从而有效地将PRC2样复合物拴在先前作用的位点上。我们的发现是，这种束缚活性的破坏导致异位H3K27me3沉积在组成型异染色质的H3K9me标记的位点处，这是出乎意料的，并证明了该系统用于获得新见解的实用性。利用C. neoformans提供了独特的机会来阐明Polycomb系统的基本特性和研究H3K27me调节在病原体适应其哺乳动物宿主中的生物学作用。为了实现这些目标，我们将1）阐明PRC2介导的基因调控的核心特性，2）定义C。3）研究Polycomb在调节新生隐翅虫毒力中的作用。这些实验将阐明这种机制的输入和表观遗传特性，这是在人类病原体中发现的第一个Polycomb系统。此外，拟议的工作将确定真菌Polycomb系统的新介质，阐明其与动物和植物对应物的关系，并进行机制研究。最后，这些研究将阐明H3K27me调节在病原体适应宿主中的作用。

 DESCRIPTION (provided by applicant): We have discovered a Polycomb repressive complex, PRC2, in the fungal meningitis pathogen Cryptococcus neoformans, that silences chromatin domains via methylation of histone H3 on lysine 27 (H3K27me). This is the first Polycomb system to be identified in a human pathogen. We propose to define the core properties and components of this system and to investigate the role of H3K27me regulation in adaptation to the host. The Polycomb silencing systems of animals and plants are critical epigenetic regulators of development that, remarkably, mediate heritable memory of prior developmental and environmental events. Polycomb systems are composed of the PRC2 complex, which catalyzes H3K27me, and the PRC1 complex, which monoubiquitylates H2A and mediates chromatin compaction. Such chromatin is also designated facultative heterochromatin because it can be dynamically regulated. The genomes of a handful of other fungi have also been reported to encode predicted PRC2 components, raising the possibility that the system functions as a general epigenetic regulator in this kingdom. We purified the five-subunit PRC2-like complex of C. neoformans and showed that it mediates subtelomeric H3K27 trimethylation (H3K27me3) and gene silencing near chromosome ends. Our studies also revealed that a chromodomain subunit of the PRC2 complex directly recognizes the H3K27me3 product of the methyltransferase, thereby effectively tethering the PRC2-like complex to the sites of previous action. Our finding that the disruption of this tethering activity results in ectopic H3K27me3 deposition at H3K9me-marked sites of constitutive heterochromatin was unexpected and demonstrates the utility of the system for obtaining new insights. The powerful genetic and biochemical tools available in C. neoformans provide unique opportunities both to elucidate the fundamental properties of a Polycomb system and to investigate the biological role of H3K27me regulation in the adaptation of a pathogen to its mammalian host. To accomplish these goals we will 1) elucidate the core properties of PRC2-mediated gene regulation, 2) define the molecular components of the C. neoformans Polycomb system, and 3) investigate the role of Polycomb in the modulation of virulence. These experiments will elucidate inputs and epigenetic properties of this mechanism, the first Polycomb system to be uncovered in a human pathogen. Furthermore, the proposed work will identify new mediators of a fungal Polycomb system, illuminate its relationship with its animal and plant counterparts, and enable mechanistic investigations. Finally, these studies will elucidate the role of H3K27me regulation in pathogen adaptation to the host.