Uncoating of a Helical Virus: Cotranslational and Coreplicational Disassembly Mechanisms

一种螺旋状病毒的剥膜：共翻译和共复制拆卸机制在动物或植物病毒感染过程的所有阶段中，病毒基因组的剥离或病毒颗粒的拆卸是最不为人所知的阶段之一。本研究考察烟草花叶病毒（TMV），因为其正义RNA基因组被封闭（封装）在棒状颗粒中。TMV颗粒被引入植物原生质体后发生双向分解。病毒RNA最初沿5′-3′方向脱包膜，该过程通过沿3′-5′方向去除包膜蛋白分子（亚基）来完成。提出了两种假设来解释这种双向拆卸：(1)在体内，脱壳始于共翻译拆卸机制，其中5‘至3’方向的亚基去除与病毒RNA的第一个ORF翻译过程中的核糖体易位一致；(2)在体内脱衣是通过共复制解体机制完成的，其中病毒聚合酶蛋白（由第一个ORF和/或其读透序列编码）参与3‘- 5’方向亚基的去除和后代负链病毒RNA分子的合成。这些假设是通过确定各种TMV突变体的行为来验证的。还将探讨聚合酶蛋白中不参与复制的区域可能需要3‘至5’分解的可能性。这项研究的意义在于它试图理解生命的一个阶段，在这个阶段中，病毒在宿主细胞中发起感染的最终成功或失败是决定的。2. 烟草花叶病毒（TMV）的非技术颗粒在接种的植物细胞中分解，使基因组得以释放，从而使子代病毒颗粒的产生得以进行，从而在宿主生物中诱导致病状态。在这一过程中，首先从病毒基因组的一端开始，按顺序去除约75%的亚基；然后从另一端取出剩余的部分。第一步可能涉及病毒蛋白的合成，另一步可能涉及病毒RNA拷贝的产生。设计实验是为了检验这些假设机制的有效性。

Shaw (University of Kentucky) EPSCOR 9726966 Uncoating of a Helical Virus: Cotranslational and Coreplicational Disassembly Mechanisms 1. Technical Of all the stages of the infection process by an animal or plant virus, uncoating of the viral genome or disassembly of the virus particle is one of the least understood. This study examines tobacco mosaic virus (TMV), as its positive-sense RNA genome is enclosed (encapsidated) in rod-shaped particles. TMV particles undergo bidirectional disassembly after being introduced into plant protoplasts. The viral RNA is initially uncoated in the 5'-to-3' direction and the process is completed by the removal of coat protein molecules (subunits) in the 3'-to-5' direction. Two hypotheses are set forth to account for the bidirectional disassembly: (1) in vivo uncoating begins by a cotranslational disassembly mechanism in which the removal of subunits in the 5'-to-3' direction is coincident with ribosome translocation during translation of the first ORF of the viral RNA; (2) in vivo uncoating is completed by a coreplicational disassembly mechanism in which the viral polymerase proteins (encoded by the first ORF and/or its readthrough sequence) are involved in the removal of subunits in the 3'-to-5' direction and the synthesis of progeny minus-strand viral RNA molecules. These hypotheses are tested by determining the behavior of various TMV mutants. The possibility that regions in the polymerase proteins that are not involved in replication may be required for 3'-to-5' disassembly will also be explored. The significance of this study lies in its atttempt to understand a stage of life in which the ultimate success or failure of a virus to initiate infection in host cells is determined. 2. Non-technical Particles of tobacco mosaic virus (TMV) disassemble in inoculated plant cells, which allows the genome to be released so that the production of progeny virus particles can proceed, inducing the pathogenic state in the host organism. In this process, about 75% of the subunits is first removed, sequentially, beginning at one end of the viral genome; the remainder is then removed proceeding from the other end. The first step may involve concomitant synthesis of viral proteins, and the other may involve the production of copies of the viral RNA. Experiments are designed to examine the validity of each of these hypothetical mechanisms.