病毒的转录过程是其生命周期的中心环节之一。包括呼肠孤病毒在内的双链RNA病毒转录过程发生在完整的内衣壳中，其RNA聚合酶利用RNA负链为模板来转录新生RNA。申请人等最近报道了一种昆虫呼肠孤病毒的转录和非转录两种状态的衣壳蛋白的近原子分辨率的电镜结构（Cheng et al., PNAS,2011,108; Yang et al., PNAS,2012,109)，但没有解析该病毒衣壳内的基因组及其RNA聚合酶的结构。此前的病毒RNA聚合酶的结构研究局限于体外表达纯化的酶的结构，未曾有人解析出病毒衣壳内基因组及其相关酶的高分辨率结构。本项目拟用冷冻电镜方法，通过改进申请人等新研制的算法来解析呼肠孤病毒非转录和转录两种状态的衣壳内基因组RNA及其聚合酶的高分辨率三维结构，以进一步阐明病毒RNA转录的分子机制。本研究已获得初步结果。最重要的是，该新重构算法可以应用到其它病毒基因组结构的解析上。

Virus transcription is one of the central phases in viral life cycle. One characteristic of the reoviruses, including most other dsRNA viruses, is that their inner capsids remain intact, and the RNA polymerases repeatedly transcribe RNA from the minus-strand RNA genome within the inner capsid. I and colleagues recently reported near-atomic resolution capsid structures of a insect reovirus in transcribing and non-transcribing states. However, we did not resolve the structures of the RNA genome and associated RNA polymerases. Previous structural analyses of viral RNA polymerases were based on the samples expressed and purified in vitro. No high resolution structures of viral genomes and associated enzymes within the capsids have been resolved previously. I propose to resolve high-resolution structures of the RNA genomes and polymerases within the transcribing and non-transcribing reoviruses by using cryo-electron microscopy and by improving our newly developed reconstruction algorithm. It aims to further elucidate the molecular mechanism of the virus RNA transcription. We have obtained initial structural results of this study. More importantly, this new algorithm can be applied to structural analysis of other virus genomes.