Function of Conserved Structures in Related Coliphage RNA's

Jacobson博士及其同事研究RNA噬菌体系统中大型基因组RNA的形状。这些分子具有双重功能：它们携带病毒基因编码的遗传信息；此外，分子远端区域之间的氢键调节病毒生长，控制病毒蛋白的表达和病毒RNA的复制。为了了解调控中使用的结构机制，将研究分子的详细构象。电子显微镜被用作主要工具。这种方法允许人们看到RNA的大结构特征，并测量由基因工程产生的突变RNA中这些结构的形状和相对稳定性的变化。观察到的结构变化可能与突变病毒生长模式的变化有关。目前的研究重点是噬菌体QB基因组RNA的构象。雅各布森博士的研究首次证明，这些分子包含两种类型的结构域。一种异常稳定；另一种是高度可变的，可以在不同的构象之间切换。这两种结构似乎都被用于病毒蛋白合成的调控。两个稳定结构域似乎抑制病毒蛋白的翻译起始。此外，稳定结构域可以作为结构锚点（很像门铰链），限制分子可变区域中替代结构的形成。此外，计算机建模将用于理解RNA构象。开发了一种新的方法来检测可能的稳定结构以及可能的可变区域的RNA分子。通过建模得到的结果与原生rna和突变rna的电镜研究一致。这种新方法引起了普遍的兴趣，并将被许多学科的研究人员使用。关于RNA结构在RNA噬菌体基因调控中的作用，仍有许多未解之谜。这些问题现在可以用现代的分析方法来解决。这些问题的答案将提供对所有大mRNA分子特性的基本见解，因此与理解植物和动物致病病毒生长、进化和基因表达调控机制有关。* * *

Jacobson 9316501 Dr. Jacobson and coworkers study the shape of large genomic RNAs in the RNA coliphage system. These molecules have a dual function: they carry the genetic information coding for viral genes; and in addition, hydrogen bonding between distant regions of the molecules regulate viral growth, controlling both the expression of viral proteins and viral RNA replication. The detailed conformation of the molecules will be studied in order to understand the structural mechanisms used in regulation. Electron microscopy is used as a primary tool. This method allows one to see large structural features in the RNA and to measure changes in the shape and relative stability of these structures in mutant RNAs that have been created by genetic engineering. The structural changes that are observed can be correlated with changes in the growth patterns of mutant viruses. The current work focuses on the conformation of genomic RNA from coliphage QB. Dr. Jacobson's studies demonstrated for the first time that the molecules contain two types of structural domains. One type is unusually stable; the other is highly variable and can switch between alternative conformations. Both types of structures appear to be utilized in the regulation of viral protein synthesis. Two of the stable domains appear to suppress translational initiation of viral proteins. In addition, stable domains may serve as structural anchors (much like door hinges) that limit the formation of alternative structures in the variable regions of the molecule. In addition, computer modeling will be used to understand RNA conformation. A new method was developed to detect likely stable structures as well as likely variable regions of an RNA molecule. The results obtained by modeling are consistent with electron microscopic studies with both native and mutant RNAs. The new approach is of general interest and will be used by investigators in many disciplines. %%% Many unanswered questions remain about the rol e of RNA structure in gene regulation in RNA coliphages. These can now be addressed with modern methods of analysis. Answers to these questions will provide fundamental insights into the properties of all large mRNA molecules, and are therefore relevant in understanding mechanisms governing growth, evolution, and the regulation of gene expression in disease causing plant and animal viruses. ***