Prion Cycle Regulation In Vivo

最近的进展表明，蛋白质物理状态的自我复制指导了发育和 传染性海绵状脑病的传播和某些表型性状的遗传 低等真核生物这种新的生物学过程，被称为朊病毒假说，预测一个独特的群体， 蛋白质的构象具有多种构象状态的能力，具有不同的生理后果 in vivo.由于单倍单功能蛋白不能发挥历史上与 核酸，如传染性和遗传，了解如何朊病毒蛋白质的结构， 限制以允许相关表型的忠实繁殖，但保持足够的灵活性， 允许偶尔的状态转换对于理解蛋白质的生理后果至关重要- 只是假设。 低等真核生物的朊病毒循环为朊病毒的研究提供了实验上易处理的模型系统 体内循环调节。例如，S.酿酒酵母是翻译的组成部分， 一种终止复合物，其功能由朊病毒循环可逆地调节。在非朊病毒状态下，Sup 35 促进有效终止（\pst]表型），但在朊病毒形式中，Sup 35的活性受到损害 导致终止密码子通读（[PSI+]表型）。而[PSI+]和[pst]表型则主要是 稳定，它们自发相互转化（~1个细胞/百万），并可通过 化学和分子刺激。 利用这个系统，我们将开始阐明近忠实的分子机制。 朊病毒形式在体内的传播主要集中在两个因素上：不同形式的相互作用 当存在于相同的细胞和有效的朊病毒转化的反式调节剂。为此，我们将 1)确定朊病毒变异体在体内优势的分子基础; 2）阐明朊病毒变异体在体内优势的分子机制 已知的Sup 35/[PS/+]朊病毒周期调节因子通过这些调节因子调节增殖和表型转变， 和3）筛选和表征新型朊病毒调节剂。总之，这些调查路线将建立一个 框架理解蛋白质只有表型繁殖方面朊病毒蛋白生物合成。一 先前工作的坚实基础表明，从朊病毒研究中收集的知识， 真核生物是明确和直接适用于我们的理解朊病毒的机制和他们的 哺乳动物的生理后果。

Recent advances suggest that self-replication of protein physical states directs both the development and spread of the Transmissible Spongiform Encephalopathies and the inheritance of some phenotypic traits in lower eukaryotes. This novel biological process, known as the prion hypothesis, predicts that a uniquegroup of proteins has the capacity to adopt multiple conformational states with distinct physiological consequences in vivo. Since one-fold-one-function proteins are unableto act in roles that have historically been linked to nucleic acids such as infectivity and inheritance, understandinghow a prion protein's structure can be constrained to allow the faithful propagation of associated phenotypes but remain sufficiently flexible to allow occasional transitions in state is crucial to understanding the physiological consequences of the protein- only hypothesis. The prion cycles of lower eukaryotesprovide experimentally tractable model systems for studyingprion cycle regulation in vivo. For example, the Sup35 protein of S. cerevisiae is a component of the translation termination complex whose function is reversibly modulatedby a prion cycle. In the non-prion state, Sup35 facilitates efficient termination (\pst] phenotype), but in the prion form, Sup35's activity is compromised leading to stop codon read-through ([PSI+] phenotype). While the [PSI+] and [pst] phenotypes are largely stable, they spontaneous interconvert (~1 cell/million) and can be induced to quantitatively switch by chemical and molecular stimuli. Using this system, we will begin to elucidate the molecular mechanism underlyingthe near-faithful propagation of prion forms in vivo by focusing on two contributingfactors: the interplay of distinct forms when present in the same cell and the trans regulators of efficient prion conversion. Toward this end, we will 1) determine the molecular basis of prion variant dominance in vivo,2) elucidate the molecular mechanisms by which knownregulators of the Sup35/[PS/+] prion cycle modulatepropagation and phenotypic transitions, and 3) screen for and characterize novel prion regulators. Together, these lines of investigation will build a framework for understandingprotein-only phenotypic propagation in terms of prion protein biogenesis. A strong foundation of previous work indicates that the knowledge gleaned from prion studies in lower eukaryotes is clearly and directly applicable to our understandingof prion mechanisms and their physiological consequences in mammals.