Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America.
Batavia Biosciences, Leiden, the Netherlands.
PLoS Biol. 2023 Jan 23;21(1):e3001693. doi: 10.1371/journal.pbio.3001693. eCollection 2023 Jan.
RNA recombination in positive-strand RNA viruses is a molecular-genetic process, which permits the greatest evolution of the genome and may be essential to stabilizing the genome from the deleterious consequences of accumulated mutations. Enteroviruses represent a useful system to elucidate the details of this process. On the biochemical level, it is known that RNA recombination is catalyzed by the viral RNA-dependent RNA polymerase using a template-switching mechanism. For this mechanism to function in cells, the recombining genomes must be located in the same subcellular compartment. How a viral genome is trafficked to the site of genome replication and recombination, which is membrane associated and isolated from the cytoplasm, is not known. We hypothesized that genome translation was essential for colocalization of genomes for recombination. We show that complete inactivation of internal ribosome entry site (IRES)-mediated translation of a donor enteroviral genome enhanced recombination instead of impairing it. Recombination did not occur by a nonreplicative mechanism. Rather, sufficient translation of the nonstructural region of the genome occurred to support subsequent steps required for recombination. The noncanonical translation initiation factors, eIF2A and eIF2D, were required for IRES-independent translation. Our results support an eIF2A/eIF2D-dependent mechanism under conditions in which the eIF2-dependent mechanism is inactive. Detection of an IRES-independent mechanism for translation of the enterovirus genome provides an explanation for a variety of debated observations, including nonreplicative recombination and persistence of enteroviral RNA lacking an IRES. The existence of an eIF2A/eIF2D-dependent mechanism in enteroviruses predicts the existence of similar mechanisms in other viruses.
正链 RNA 病毒中的 RNA 重组是一种分子遗传学过程,它允许基因组最大程度地进化,并且对于稳定基因组免受积累突变的有害影响可能是必不可少的。肠道病毒是阐明该过程细节的有用系统。在生化水平上,已知 RNA 重组是由病毒 RNA 依赖性 RNA 聚合酶通过模板转换机制催化的。为了使该机制在细胞中起作用,重组基因组必须位于同一亚细胞隔室中。病毒基因组如何被运送到与膜相关且与细胞质隔离的基因组复制和重组部位尚不清楚。我们假设基因组翻译对于重组的基因组共定位是必不可少的。我们表明,完全抑制供体肠道病毒基因组内部核糖体进入位点(IRES)介导的翻译会增强重组,而不是损害重组。重组不是通过非复制机制发生的。相反,基因组非结构区的翻译足够多,足以支持随后发生的重组所需的步骤。非规范翻译起始因子 eIF2A 和 eIF2D 对于 IRES 非依赖性翻译是必需的。我们的结果支持在 eIF2 依赖性机制失活的情况下,eIF2A/eIF2D 依赖性机制的存在。肠道病毒基因组 IRES 非依赖性翻译机制的发现为各种有争议的观察结果提供了一种解释,包括非复制性重组和缺乏 IRES 的肠道病毒 RNA 的持续存在。肠道病毒中存在 eIF2A/eIF2D 依赖性机制预示着其他病毒中也存在类似的机制。