Translational Control of Morphology and Virulence in Candida albicans

项目摘要/摘要 白色念珠菌是人类最常见的真菌病原体，可引起多种 全身和粘膜感染。免疫受损的个人，包括癌症患者 化疗、艾滋病患者、新生儿和器官移植接受者特别容易患上 感染。白念珠菌从单一发芽酵母经历可逆形态转变的能力 细胞到细丝(细长的细胞端到端连接)对毒力以及几种毒力都很重要- 相关属性。虽然控制白念珠菌的转录和翻译后机制 形态转换已经得到了很好的描述，但对它的作用却知之甚少 翻译机制。我们最近发现UME6，它编码一种关键的细丝特异的 白念珠菌形态和毒力的转录调控因子，拥有最长的5‘ 迄今为止在真菌中发现的非翻译区(UTRs)。UME6 5‘非编码区抑制白色念珠菌丝状化 在各种诱导条件下以及UME6的表达能力对白念珠菌的影响 形态学。5‘非编码区不影响UME6转录水平或诱导动力学，而是特异性地 降低UME6的翻译效率，这是由多聚体图谱分析确定的。重要的是， UME6 5‘非编码区的翻译抑制水平受不同微丝诱导的调控 条件。最近的一项初步核糖体图谱实验表明，存在两个不同的核糖体 UME6 5‘UTR中的失速地点，这两个地点都位于预测综合体的上游 稳定的RNA二级结构。RNA-seq分析表明，除了UME6外，还有一种 大量白念珠菌基因参与丝状化，以及其他各种毒力相关 包括生物膜的形成、黏附和分泌降解酶的产生等过程也具有 长长的5‘UTR。基于这一证据，我们的假设是5‘非编码区介导的翻译效率 机制在控制白色念珠菌的形态、毒力和毒力相关方面发挥着重要作用 响应宿主环境提示的过程。为了解决这一假设，我们计划：1) 确定白念珠菌丝状生长信号通路如何控制形态和Ume6的表达 通过5‘非编码区调节UME6的翻译效率，2)通过以下方式确定分子机制(S) UME6的5‘非编码区抑制了翻译效率，3)决定了5’非编码区介导的更广泛的作用 控制白念珠菌毒力及多种毒力相关基因的翻译效率机制 属性。这些研究将有助于更好地理解5‘非翻译区是如何影响翻译效率的 机制控制着人类主要真菌病原体的形态和毒力。归根结底，共同的 调节真菌致病性的翻译效率机制的真菌特异性成分可能 作为开发新的和更有效的抗真菌策略的潜在目标。

PROJECT SUMMARY/ABSTRACT Candida albicans, the most commonly isolated human fungal pathogen, is responsible for a wide variety of systemic and mucosal infections. Immunocompromised individuals, including cancer patients on chemotherapy, AIDS patients, neonates, and organ transplant recipients, are particularly susceptible to infection. The ability of C. albicans to undergo a reversible morphological transition from single budding yeast cells to filaments (elongated cells attached end-to-end) is important for virulence as well as several virulence- related properties. While transcriptional and post-translational mechanisms that control the C. albicans morphological transition have been well-characterized, considerably less is known about the role of translational mechanisms. We have recently discovered that UME6, which encodes a key filament-specific transcriptional regulator of C. albicans morphology and virulence, possesses one of the longest 5’ untranslated regions (UTRs) identified in fungi to date. The UME6 5’ UTR inhibits C. albicans filamentation under a variety of inducing conditions as well as the ability of UME6 expression to determine C. albicans morphology. The 5’ UTR does not affect UME6 transcript levels or induction kinetics, but instead specifically reduces translational efficiency of UME6, as determined by a polysome profiling analysis. Importantly, the level of translational inhibition directed by the UME6 5’ UTR is modulated by different filament-inducing conditions. A recent preliminary ribosome profiling experiment indicates the presence of two distinct ribosome stalling sites in the UME6 5’ UTR, both of which are located immediately upstream of predicted complex stable RNA secondary structures. An RNA-seq analysis has demonstrated that in addition to UME6, a significant number of C. albicans genes involved in filamentation, and a variety of other virulence-related processes, including biofilm formation, adhesion, and secreted degradative enzyme production, also possess long 5’ UTRs. Based on this evidence, our hypothesis is that 5’ UTR-mediated translational efficiency mechanisms play an important role in controlling C. albicans morphology, virulence and virulence-related processes in response to host environmental cues. In order to address this hypothesis, we plan to: 1) determine how C. albicans filamentous growth signaling pathways control morphology and Ume6 expression by regulating UME6 translational efficiency via the 5’ UTR, 2) determine the molecular mechanism(s) by which the UME6 5’ UTR inhibits translational efficiency, 3) determine the broader role of 5’ UTR-mediated translational efficiency mechanisms in controlling C. albicans virulence and a variety of virulence-related properties. These studies will provide a better understanding of how 5’ UTR-mediated translational efficiency mechanisms control morphology and virulence in a major human fungal pathogen. Ultimately, common fungal-specific components of translational efficiency mechanisms that regulate fungal pathogenicity could serve as potential targets for the development of novel and more effective antifungal strategies.