PAS Domain Protein Pas3 Interacts with the Chromatin Modifier Bre1 in Regulating Cryptococcal Morphogenesis.
PAS Domain Protein Pas3 Interacts with the Chromatin Modifier Bre1 in Regulating Cryptococcal Morphogenesis.
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作者：
Zhao Y;Upadhyay S;Lin X
对于无处不在的环境病原体新型隐球菌而言，从酵母形态到丝状形态的转变使其对土壤变形虫等天然捕食者具有抵抗力，并且是产生传染性孢子的一个不可或缺的分化事件。有趣的是，丝状化具有免疫刺激作用，并会减弱新型隐球菌在哺乳动物宿主中的毒力。一致地，形态发生转录因子Znf2对新型隐球菌与各种宿主的相互作用有着深远的影响。因此，确定激活丝状化的信号通路有助于更好地理解新型隐球菌的生物学特性。在这项研究中，我们鉴定出一种PAS结构域蛋白Pas3，它在调节新型隐球菌丝状化过程中位于Znf2的上游发挥作用。有趣的是，Pas3在细胞核中与染色质修饰因子Bre1相互作用，以调节Znf2及其主要下游靶点的转录水平。这是PAS结构域信号调节因子与染色质修饰因子相互作用，通过影响新型隐球菌转录组来控制丝状化的首个实例。
在许多微生物中，不同形态类型之间的转换是一种适应性细胞反应。在新型隐球菌中，从酵母到菌丝的转变使其对土壤中的微生物捕食具有抵抗力，并且是其生命周期的一个组成部分。形态发生也已知与毒力相关，丝状形态在新型隐球菌病的哺乳动物模型中具有免疫刺激和保护作用。先前的研究已确定转录因子Znf2是新型隐球菌丝状化的主要调节因子。然而，Znf2的上游调节因子在很大程度上仍然未知。PAS结构域蛋白长期以来被认为是多种环境信号的转导器。在此，我们鉴定出一种PAS结构域蛋白Pas3作为Znf2的上游调节因子。令人惊讶的是，这个小的Pas3蛋白缺乏核定位信号，但在细胞核中富集，在那里它调节ZNF2及其主要下游靶点的转录水平。我们发现PAS结构域对Pas3的核富集和功能至关重要。有趣的是，Pas3与Bre1相互作用，Bre1是新型隐球菌组蛋白H2B单泛素化（H2Bub1）和H3赖氨酸4二甲基化（H3K4me2）所必需的，这两种组蛋白修饰已知与活跃的基因转录相关。事实上，基于功能缺失、上位性和转录组分析，Bre1与Pas3一起在调节新型隐球菌丝状化中发挥作用。这些发现提供了信号调节因子与染色质修饰因子共同作用以控制新型隐球菌丝状化的首个证据。
For the ubiquitous environmental pathogen Cryptococcus neoformans, the morphological transition from yeast to filament confers resistance to natural predators like soil amoeba and is an integral differentiation event to produce infectious spores. Interestingly, filamentation is immuno-stimulatory and attenuates cryptococcal virulence in a mammalian host. Consistently, the morphogenesis transcription factor Znf2 profoundly shapes cryptococcal interaction with various hosts. Identifying the signaling pathways activating filamentation is thus, conductive to a better understanding of cryptococcal biology. In this study, we identified a PAS domain protein Pas3 that functions upstream of Znf2 in regulating cryptococcal filamentation. Interestingly, Pas3 interacts with the chromatin modifier Bre1 in the nucleus to regulate the transcript level of Znf2 and its prominent downstream targets. This is the first example of a PAS domain signaling regulator interacting with a chromatin modifier to control filamentation through their impact on cryptococcal transcriptome. Switching between different morphotypes is an adaptive cellular response in many microbes. In Cryptococcus neoformans, the yeast-to-hypha transition confers resistance to microbial predation in the soil and is an integral part of its life cycle. Morphogenesis is also known to be associated with virulence, with the filamentous form being immune-stimulatory and protective in mammalian models of cryptococcosis. Previous studies identified the transcription factor Znf2 as a master regulator of cryptococcal filamentation. However, the upstream regulators of Znf2 remain largely unknown. PAS domain proteins have long been recognized as transducers of diverse environmental signals. Here, we identified a PAS domain protein Pas3 as an upstream regulator of Znf2. Surprisingly, this small Pas3 protein lacks a nuclear localization signal but is enriched in the nucleus where it regulates the transcript level of ZNF2 and its prominent downstream targets. We discovered that the PAS domain is essential for Pas3’s nuclear enrichment and function. Intriguingly, Pas3 interacts with Bre1, which is required for Cryptococcus histone H2B monoubiquitination (H2Bub1) and H3 lysine 4 dimethylation (H3K4me2), two histone modifications known to be associated with active gene transcription. Indeed, Bre1 functions together with Pas3 in regulating cryptococcal filamentation based on loss-of-function, epistasis, and transcriptome analysis. These findings provide the first evidence of a signaling regulator acting with a chromatin modifier to control cryptococcal filamentation.