Biology of Circoviruses

背景资料。 圆环病毒是一种小的、无包膜的二十面体病毒，是几个动物物种的重要病原体。鸡传染性贫血是由一种名为鸡贫血病毒(CAV)的圆环病毒引起的。在集约化家禽养殖期间控制CAV的暴发是代价高昂且具有破坏性的。圆环病毒基因组很小，从1.7-2.3kb到圆形，这就是这个科的名字。CAV仅编码3个开放阅读框(ORF)。病毒在鸡中的致病性是由于一个单一的开放阅读框架，命名为病毒蛋白3(VP3)，它导致感染细胞的广泛凋亡，是病毒有效复制所必需的。为了了解CAV-VP3是如何诱导细胞死亡的，我们课题组纯化了与该蛋白相关的细胞蛋白复合体，发现CAV-VP3与后期促进复合体/环体(APC/C)结合。包括乳头瘤病毒、腺病毒、疱疹病毒、痘病毒和圆环病毒在内的几种不同类型的病毒都被证明具有结合和灭活APC/C的蛋白质。尽管这些广泛的病毒已经收敛地进化出抑制APC/C的策略，但这种相互作用在病毒复制过程中的功能重要性尚不清楚。因此，对CAV生物学的继续研究可以为分子病毒学和细胞生物学的一般机制提供基本的见解。 研究计划。 我们以前的研究主要集中在冠状病毒VP3蛋白的细胞毒性机制上。我们发现CAV-VP3与细胞周期和DNA损伤反应通路的关键成分相互作用。我们现在计划通过研究CAV-VP3的这些特性如何增强病毒的复制和传播来继续我们的研究计划。 明确的目标。 目的1.病毒复制所需的CAV-VP3蛋白的功能。 我们的研究表明，CAV-VP3的核质穿梭和多聚体活性是其细胞毒特性所必需的。我们将利用CAV的体外复制系统来评估CAV-VP3的每一种活性对复制的影响。 目的2.CAV-VP3与APC/C相互作用在病毒复制中的作用。 CaV-VP3相互作用并抑制后期促进复合体(APC)，APC是细胞周期调控机制的关键组成部分。在这个目标中，我们将研究抑制APC如何促进病毒复制。 目的3.CAV-VP3蛋白作为DNA损伤感受器和DNA损伤反应的调节器。 我们观察到CAV-VP3能够减弱细胞DNA损伤反应。在最终目标中，我们将研究CAV-VP3是如何被DNA损伤信号通路靶向的，以及这些相互作用对于有效的病毒复制的重要性。

BACKGROUND. Circoviruses are small, non-enveloped icosahedral viruses that are important pathogens of several animal species. Infectious chicken anemia, is caused by a circovirus called chicken anemia virus (CAV). Controlling outbreaks of CAV during intensive poultry farming is costly and disruptive. Circovirus genomes are small, ranging between 1.7-2.3 kb and circular, which gives the family its name. CAV encodes only 3 open reading frames (ORFs). Pathogenicity of the virus in chickens is due to a single ORF, designated viral protein 3 (VP3), which causes extensive apoptosis in infected cells and is required for efficient viral replication. In order to understand how CAV-VP3 induces cell death, our group purified the cellular protein complexes associated with this protein and found that CAV-VP3 binds to the anaphase promoting complex/cyclosome (APC/C). Several diverse types of virus including Papillomavirus, Adenovirus, Herpesvirus, Poxvirus and Circovirus have all been shown to have proteins that bind and inactivate the APC/C. Although this wide range of viruses have convergently evolved strategies to inhibit the APC/C, the functional importance of this interaction during viral replication is unknown. Continued study of the biology of CAV can therefore provide fundamental insights into general mechanisms of molecular virology and cell biology. RESEARCH PROGRAM. Our previous studies focused on the mechanism of cytotoxicity of the VP3 protein of CAV. We found that CAV-VP3 interacts with critical components of the cell cycle and DNA damage response pathway. We now plan to continue our research program by examining how these properties of CAV-VP3 enhance viral replication and spread. SPECIFIC AIMS. Aim 1. Functions of the CAV-VP3 protein required for efficient viral replication. Our studies have shown that nuclocytoplasmic shuttling and multimerization activity of CAV-VP3 is required for the cytotoxic properties of the protein. We will utilize an in vitro replication system of CAV to assess the impact of each of these activities of CAV-VP3 on replication. Aim 2. The role the CAV-VP3 interaction with the APC/C in viral replication. CAV-VP3 interacts and inhibits the anaphase-promoting complex (APC), a critical component of the cell cycle regulatory machinery. In this aim we will study how inhibition of the APC promotes viral replication. Aim 3. The CAV-VP3 protein as a DNA damage sensor and modulator of DNA damage responses. We have observed that CAV-VP3 is able to attenuate cellular DNA damage responses. In the final aim we will study how CAV-VP3 is targeted by the DNA damage signaling pathway and the importance of these interactions for efficient viral replication.