Processing and Function of Polyoma RNA

描述（由申请人提供）：多瘤病毒将继续作为研究哺乳动物细胞RNA代谢的模型系统。我们将进行大量的研究，以了解病毒DNA合成开始前大多数早期链mrna到开始后大多数晚期链mrna的转变。重点将放在RNA编辑上。我们发现，早期和晚期链RNA水平的调控都是转录后的，而晚期链RNA水平的调控以一种意想不到的方式进行：聚腺苷酸化在后期是低效的，导致mrna积累，因为它们可以更有效地剪接。我们最近发现，这种调节似乎涉及到后期多聚(A)信号的编辑，我们建议通过一些研究来跟踪这些观察结果，以检查这种情况是如何发生的。在相关工作中我们发现，早期链基因表达的调控是通过核反义RNA进行的，细胞可能普遍利用核反义RNA来调控自身许多基因的表达。因此，这种病毒提供了一个强大的遗传和生化系统来研究反义调控，并学习如何利用这种知识来调节其他基因的表达。我们已经证明，在存在后链反义分子的情况下，许多核早链rna被ADAR1酶编辑。此外，我们发现对这种酶广泛编辑的dsrna似乎有两种核反应。首先，一个由三种蛋白质（p54nrb、PSF和matrin 3）组成的复合物可以与混杂编辑的rna协同结合，并阻止它们输出到细胞质。其次，vigilin蛋白与编辑过的rna结合，并通过一种涉及细胞DNA修复机制成分的新途径导致异色基因沉默的建立。我们建议更详细地研究这些新发现的反应途径，特别是在多瘤感染的背景下。

DESCRIPTION (provided by applicant): Polyoma virus will continue to serve as a model system to study RNA metabolism in mammalian cells. We will perform a number of studies designed to understand the switch from mostly early-strand mRNAs before the initiation of viral DNA synthesis to mostly late-strand mRNAs afterwards. The focus will be on RNA editing. We have found that the regulation of both early and late strand RNA levels is post-transcriptional, and late-strand RNA levels are regulated in an unexpected way: polyadenylation is inefficient at late times, leading to mRNAs that accumulate because they can be spliced more efficiently. We recently discovered that this regulation appears to involve editing of the late poly(A) signal, and we propose to follow up these observations with a number of studies to examine how this occurs. In related work we have found that the regulation of early-strand gene expression is by nuclear antisense RNA, which is likely to be generally used by cells to regulate the expression of many of their own genes. This virus thus provides a powerful genetic and biochemical system in which to study antisense regulation and to learn how to exploit this knowledge to regulate the expression of other genes. We have shown that in the presence of late-strand antisense molecules, many nuclear early-strand RNAs are edited by the enzyme ADAR1. Further, we have discovered that there appear to be two nuclear responses to dsRNAs that have been extensively edited by this enzyme. First, a complex of three proteins (p54nrb, PSF and matrin 3) can bind cooperatively to promiscuously edited RNAs and prevent their export to the cytoplasm. Second, the protein vigilin binds to edited RNAs and can lead to the establishment of heterochromatic gene silencing through a novel pathway that involves components of the cellular DNA repair machinery. We propose to examine each of these newly-discovered response pathways in more detail, and especially in the context of polyoma infection.