Packaging and Structure of Viral Genomes

描述（由申请人提供）：成熟病毒的形成是一个重要的研究领域，不仅因为我们对病毒本身的了解，而且因为病毒是阐明大型大分子复合物组装背后的基本原理的简单模型系统。本文提出了一种结合建模和实验的方法来研究两种小的、无包膜的二十面体病毒。噬菌体将它们的双链DNA基因组包装到预先形成的蛋白质衣壳中，利用atp驱动的马达来克服反对包装的静电、弹性和熵力。相比之下，单链RNA病毒自发组装，蛋白质衣壳在RNA基因组的外部形成，而不需要消耗能量。我们将继续研究噬菌体中DNA包装的结构和热力学方面，重点研究DNA-DNA和DNA-衣壳的相互作用，以及DNA扭结。我们还将对非病毒系统中反对高密度DNA压实的力量进行调查。从这些工作中学到的原理将对理解基因组结构和原核和真核细胞中基因表达的调控具有重要意义。我们对RNA病毒的研究将包括开发改进的卫星烟草花叶病毒（STMV）和pariacoto病毒（PaV）的三维模型；RNA病毒组装建模方法的发展；以及聚合RNA缩聚的实验研究，特别是碱性多肽。RNA病毒的研究是基于这样一种假设，即组装是由带正电荷的多肽和带负电荷的RNA之间强烈但非特异性的相互作用引发的，这种相互作用导致类似于浓缩DNA的聚合体坍塌，随后形成成熟的病毒。如果正确，这一假设可以为新药设计策略提供基础。这一结果很可能也适用于其他大型rna -蛋白质组装体的形成。

DESCRIPTION (provided by applicant): The formation of mature viruses is an important research area, not only because of what we learn about the viruses themselves, but because viruses are simple model systems for elucidating the fundamental principles behind the assembly of large macromolecular complexes. This proposal presents a combined modeling and experimental approach to the investigation of two kinds of small, unenveloped, icosahedral viruses. Bacteriophages package their double-stranded DNA genomes into preformed protein capsids, using an ATP-driven motor to overcome the electrostatic, elastic and entropic forces that oppose packaging. In contrast, single-stranded RNA viruses assemble spontaneously, with the protein capsid forming around the outside of the RNA genome without the expenditure of energy. We will continue our investigations of the structural and thermodynamic aspects of DNA packaging in bacteriophage, focusing our efforts on DNA-DNA and DNA-capsid interactions, and on DNA kinking. We will also undertake an investigation of the forces opposing the compaction of DNA to high density in non-viral systems. The principles learned from these efforts will have implications for the understanding of genome structures and the regulation of gene expression in both prokaryotic and eukaryotic cells. Our investigations on RNA viruses will include the develop of improved three-dimensional models for satellite tobacco mosaic virus (STMV) and pariacoto virus (PaV); the development of methods for modeling assembly of RNA viruses; and experimental investigations of the condensation of RNA by polycations, particularly basic polypeptides. The work on RNA viruses is based on the hypothesis that assembly is initiated by strong but nonspecific interactions between positively charged polypeptides and the negatively charged RNA, leading to a collapsed aggregate resembling condensed DNA, followed by the formation of the mature virus. If correct, this hypothesis could provide the basis for new drug design strategies. The results might well apply to the formation of other large RNA-protein assemblies as well. PUBLIC HEALTH RELEVANCE Viruses cause many human diseases. An understanding of how they are assembled would offer important opportunities for the development of new antiviral drugs. In addition, bacteriophage (viruses that infect bacteria) have been used occasionally in the past to treat bacterial infections in humans. Knowledge about bacteriophage assembly could prove useful in the design of new antibacterial agents.