Laboratory of Organic Chemistry, Eidgenössische Technische Hochschule Zürich, 8093 Zürich, Switzerland.
Laboratory of Organic Chemistry, Eidgenössische Technische Hochschule Zürich, 8093 Zürich, Switzerland
Proc Natl Acad Sci U S A. 2018 May 22;115(21):5432-5437. doi: 10.1073/pnas.1800527115. Epub 2018 May 7.
Viruses are remarkable nanomachines that efficiently hijack cellular functions to replicate and self-assemble their components within a complex biological environment. As all steps of the viral life cycle depend on formation of a protective proteinaceous shell that packages the DNA or RNA genome, bottom-up construction of virus-like nucleocapsids from nonviral materials could provide valuable insights into virion assembly and evolution. Such constructs could also serve as safe alternatives to natural viruses for diverse nano- and biotechnological applications. Here we show that artificial virus-like nucleocapsids can be generated-rapidly and surprisingly easily-by engineering and laboratory evolution of a nonviral protein cage formed by lumazine synthase (AaLS) and its encoding mRNA. Cationic peptides were appended to the engineered capsid proteins to enable specific recognition of packaging signals on cognate mRNAs, and subsequent evolutionary optimization afforded nucleocapsids with expanded spherical structures that encapsulate their own full-length RNA genome in vivo and protect the cargo molecules from nucleases. These findings provide strong experimental support for the hypothesis that subcellular protein-bounded compartments may have facilitated the emergence of ancient viruses.
病毒是高效的纳米机器，能够在复杂的生物环境中劫持细胞功能，复制和自我组装其组件。由于病毒生命周期的所有步骤都依赖于形成保护性的蛋白质外壳，将 DNA 或 RNA 基因组包装在内，因此从非病毒材料中自上而下构建类似病毒的核衣壳可以为病毒粒子组装和进化提供有价值的见解。这些构建体还可以作为天然病毒的安全替代品，用于各种纳米和生物技术应用。在这里，我们展示了通过工程设计和实验室进化由光氨酸合酶（AaLS）及其编码的 mRNA 形成的非病毒蛋白笼，可以快速且出人意料地轻松生成人工类似病毒的核衣壳。阳离子肽被添加到工程化的衣壳蛋白上，以实现对同源 mRNA 上包装信号的特异性识别，随后的进化优化使核衣壳具有扩展的球形结构，在体内封装其自身全长的 RNA 基因组，并保护货物分子免受核酸酶的侵害。这些发现为这样的假设提供了强有力的实验支持，即细胞内的蛋白质结合隔室可能促进了古老病毒的出现。
