Heritable yeast prions have a highly organized three-dimensional architecture with interfiber structures
Heritable yeast prions have a highly organized three-dimensional architecture with interfiber structures
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DOI：
10.1073/pnas.1211976109
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发表时间：
2012-09-11
影响因子：
11.1
通讯作者：
Frangakis, Achilleas S.
中科院分区：
文献类型：
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作者：
Saibil, Helen R.;Seybert, Anja;Frangakis, Achilleas S.
酵母朊病毒构成了一种“纯蛋白质”遗传机制，被野生酵母广泛使用以产生不同的表型。最具特征的朊病毒之一，[PSI+]，是由Sup 35朊病毒结构域的构象变化，一个预防终止因子。当这个结构域从其正常的可溶性形式转变为不溶性淀粉样蛋白时，随之而来的蛋白质合成的变化就会产生新的性状。两个因素使这些特征可遗传：（i）淀粉样蛋白构象是自我模板化的;（ii）蛋白质重塑因子热休克蛋白（Hsp）104（与Hsp 70分子伴侣一起作用）以高保真度将模板分配给子细胞。由其他几种酵母蛋白形成的朊病毒产生它们自己的表型，但共享相同的遗传机制基础。除了淀粉样纤维本身，这些基于蛋白质的遗传因素的细胞结构是未知的。为了研究朊病毒组件在其细胞环境中的3D排列，我们研究了酵母[PSI+]朊病毒在本地，水合状态原位，利用最近开发的玻璃化细胞冷冻切片的方法。玻璃化切片的冷冻电子断层扫描显示，朊病毒组装体是细胞质中规则间隔的原纤维排列成束，没有边界结构。虽然纤维的间距很大，但其他细胞复合物，如核糖体，被排除在原纤维阵列之外。亚断层图像平均，使有组织的性质的组件，揭示了一个额外的阵列之间的纤维密度的存在。我们认为这些结构构成了一种自组织机制，协调纤维沉积和朊病毒遗传的调节。
Yeast prions constitute a "protein-only" mechanism of inheritance that is widely deployed by wild yeast to create diverse phenotypes. One of the best-characterized prions, [PSI+], is governed by a conformational change in the prion domain of Sup35, a translation-termination factor. When this domain switches from its normal soluble form to an insoluble amyloid, the ensuing change in protein synthesis creates new traits. Two factors make these traits heritable: (i) the amyloid conformation is self-templating; and (ii) the protein-remodeling factor heat-shock protein (Hsp)104 (acting together with Hsp70 chaperones) partitions the template to daughter cells with high fidelity. Prions formed by several other yeast proteins create their own phenotypes but share the same mechanistic basis of inheritance. Except for the amyloid fibril itself, the cellular architecture underlying these protein-based elements of inheritance is unknown. To study the 3D arrangement of prion assemblies in their cellular context, we examined yeast [PSI+] prions in the native, hydrated state in situ, taking advantage of recently developed methods for cryosectioning of vitrified cells. Cryo-electron tomography of the vitrified sections revealed the prion assemblies as aligned bundles of regularly spaced fibrils in the cytoplasm with no bounding structures. Although the fibers were widely spaced, other cellular complexes, such as ribosomes, were excluded from the fibril arrays. Subtomogram image averaging, made possible by the organized nature of the assemblies, uncovered the presence of an additional array of densities between the fibers. We suggest these structures constitute a self-organizing mechanism that coordinates fiber deposition and the regulation of prion inheritance.