Regulation of Virus Capsid Assembly

乙型肝炎B病毒（HBV）是一种有包膜的dsDNA病毒，具有ssRNA中间形式。正确组装 HBV的二十面体核心是复制所必需的。RNA前基因组的逆转录 pgRNA（pgRNA）在完整的衣壳（核心的蛋白质壳）内发生。HBV衣壳是 由120个衣壳蛋白（Cp）二聚体构建。在体外，Cp自发组装。在体内，pgRNA是 在大量过量的宿主RNA存在下，即使Cp在宿主细胞中表达， 译很难想象有什么选择性，特别是考虑到RNA结合上的+17电荷， Cp的域。什么可以防止误装配？基于我们的体外研究，我们开发了 假设HBV装配是变构调节：我们认为Cp具有装配活性， 无活性构象。我们已经确定了不同的盐和小分子，有利于或抑制组装。 我们还鉴定了一些抑制和增强组装的突变。与此同时， 频率，天然发生的Cp突变，与产量的意外变化相关， 我们假设这些突变影响装配能力。为了更好地理解 调节HBV组装，我们建议测试我们的假设，（i）体外组装可以相关 在体内组装和（ii）组装受到变构调节。公共自然集会 发生的突变体将与表型相关。对于装配缺陷Cp，我们将描述结构 Cp二聚体和衣壳中Cp结合之间的差异，变构的基本预测。我们将 研究二聚体界面的突变如何影响组装;通常，亚基之间的界面是 通过变构转换改变。我们将研究Cp的RNA结合和特异性。我们的初步数据 变构的可能性很大，但需要进一步研究。我们对HBV的研究结果将提出以下问题： 在其他病毒中组装是如何调节的。 超过3.5亿人患有慢性B肝炎病毒（HBV）感染，其中包括更多 超过125万美国人。在全球范围内，HBV今年将导致100万人死亡。通过确定 HBV装配是如何调节的，我们将描述抗病毒干预的新靶点。

Hepatitis B virus (HBV) is an enveloped dsDNA virus with a ssRNA intermediate form. Correct assembly of the icosahedral core of HBV is required for replication. Reverse transcription of the RNA pre-genome (pgRNA) takes place within the completed capsid, the protein shell of the core. The HBV capsid is constructed from 120 capsid protein (Cp) dimers. In vitro, Cp assembles spontaneously. In vivo, pgRNA is selectively encapsidated in the presence of a great excess of host RNA, even when the Cp is expressed in trans. It is hard to imagine how there can be any selectivity, especially given the +17 charge on the RNAbinding domain of Cp. What prevents misassembly? Based on our in vitro studies, we have developed the hypothesis that HBV assembly is allosterically regulated: we suggest that Cp has assembly-active and - inactive conformations. We have identified different salts and small molecules that favor or inhibit assembly. We have also identified a number of mutations that inhibit and enhance assembly. In parallel, there are high frequency, naturally occurring mutations of the Cp that correlate with unexpected changes in the yield of virions; we hypothesize that these mutations affect assembly proficiency. In order to better understand regulation of HBV assembly, we propose to test our hypotheses that (i) in vitro assembly can be correlated with assembly in vivo and (ii) assembly is subject to allosteric regulation. Assembly of the common naturally occurring mutants will be correlated with phenotype. With assembly-defective Cp, we will describe structural differences between Cp dimers and Cp bound in capsids, a fundamental prediction of allostery. We will investigate how mutations at the dimer interface affect assembly; typically, interfaces between subunits are altered by allosteric transitions. We will examine the RNA-binding and specificity of Cp. Our preliminary data for allostery is strong but requires further investigation. Our results with HBV will advance the question of how assembly is regulated in other viruses. More than 350 million individuals suffer from chronic infection with hepatitis B virus (HBV), including more than 1.25 million Americans. Worldwide, HBV will contribute to 1 million deaths this year. By determining how HBV assembly is regulated, we will characterize a new target for antiviral intervention.