YEAST PRION FACTOR (PSI+)

某些神经退行性疾病，如羊瘙痒病、疯牛病 和人类的克雅氏病，似乎是通过一种 不含任何核酸的有感染性的蛋白质，称为Pron。普里恩， 被认为是一种细胞蛋白质的改变形式，它可以将 将正常蛋白(PrPC)转变为PrPSc构象。近期 有证据表明，普恩病毒并不局限于特征良好的 哺乳动物的情况下，但这两种酵母蛋白也可以承担自我 传播“普里恩”构象。因此，遗传变异性的运作 仅仅在蛋白质构象水平上可能是一种广泛使用的机制 继承的权利。酵母菌是研究细菌的理想生物。 Pron遗传形式的基础知识。因此，详细的遗传和 酵母菌[PSI+]因子的生化研究 Sup35p=真核释放因子eRF3)。 不同的瘙痒病菌株的存在，这表明 病毒核酸的突变，挑战了Pron假说。 酵母[PSI+]蛋白的类似变体，这是不可能的 由病毒引起，最近为这项研究获得了支持 认为不同的Pron菌株对应于不同的自我 繁殖普恩蛋白构象。[ETA+]因子，之前 被PI发现，将被调查以确定它是否是 新的Prion或[PSI+]Prion的变体。具有提示性的证据表明 Sup35p的不同功能构象(即[psi-])的存在， 其中一些也是自繁殖的普恩，将被探索。这个 所有[Psi+]和[Psi-]变体的生化特性及其规律 管理它们的遗传和遗传相互作用的因素将被定义。 对哺乳动物蛋白菌株的类似遗传分析将会多得多 很难。 [PSI]朊蛋白Sup35p的结构/功能分析 也将被承担。能够和不能诱导的Sup35p小肽 将获得[PSI+]，以标记[PSI+]中涉及的Sup35p区域 诱导和维护。将获得SUP35的突变 刺激[PSI+]的自发出现，因此类似 哺乳动物普恩基因的“家族性”突变。哺乳动物 家族性突变似乎增加了正常折叠的倾向 PrPC蛋白翻转到普里恩构象，从而导致 普里恩病。SUP35的新等位基因可阻止Sup35蛋白 在没有[PSI+]“种子”的情况下变为[PSI+]也将是 获得并表征了。 最后，影响[PSI+]诱导或繁殖的新基因 将鉴定普恩病毒和几个已知的与SUP35相互作用的基因 将专门测试它们对[PSI+]的影响。

Certain neurodegenerative diseases, such as sheep scrapie, mad cow disease and Creutzfeldt-Jacob disease in humans, appear to be transmitted by an infectious protein, called a prion, without any nucleic acid. The prion, is proposed to be an altered form of a cellular protein which can convert the normal protein (PrPC) into its prion PrPSc) conformation. Recent evidence indicates what prions are not limited to the well characterized mammalian case, but that two yeast proteins can also take on self- propagating "prion" conformations. Thus, genetic variability operating solely at the level of protein conformation may be a widely used mechanism of inheritance. Yeast is an ideal organism in which to investigate the basics of the prion form of inheritance. Thus, detailed genetic and biochemical studies of the yeast [PSI+] factor, which is a prion form of the Sup35p=eukaryotic release factor eRF3), are proposed. The existence of different scrapie strains, which are suggestive of mutations in viral nucleic acid, has challenged the prion hypothesis. Analogous variants of the yeast [PSI+] prion, that could not have been caused by viruses, have recently been obtained for this study, supporting the view that different prion strains correspond to distinct self- propagating prion protein conformations. The [ETA+] factor, previously discovered by the PI, will be investigated to determine whether it is a new prion or a variant of the [PSI+] prion. Suggestive evidence for the existence of different functional (i.e. [psi-]) conformations of Sup35p, some of which are also self-propagating prions, will be explored. The biochemical properties of all [PSI+] and [psi-] variants and the rules that govern their inheritance and genetic interactions will be defined. Similar genetic analyses of mammalian prion strains would be much more difficult. A structure/function analysis of the [PSI] prion protein, Sup35p, will also be undertaken. Small peptides of Sup35p that can and cannot induce [PSI+], will be obtained to mark regions of Sup35p involved in [PSI+] induction and maintenance. Mutations in SUP35 will be obtained that stimulate the spontaneous appearance of [PSI+] and are therefore analogous to "familial" mutations in the mammalian prion gene. The mammalian familial mutations appear to increase the inclination of normally folded PrPC protein to flip into the prion conformation, thereby causing the prion disease. New alleles of SUP35 that prevent the Sup35 protein from becoming [PSI+] in the presence of absence of [PSI+] "seeds" will also be obtained and characterized. Finally, new genes that affect the induction or propagation of the [PSI+] prion will be identified and several genes known to interact with SUP35 will be specifically tested for their effects on [PSI+].