UV-INDUCED INHIBITION OF SMALL NUCLEAR RNA SYNTHESIS

我们正在研究紫外线辐射的一些新的影响，这是一种主要的环境 动物细胞中的致癌物和诱变剂。紫外光诱导出两种独特的 抑制小核糖核酸(SnRNA)合成的不同类型 种U1，U2，U3，U4和U5。(U1、U2和U4 RNA，可能还有U5 RNA， 每一个都有基本的功能。)U单链RNA合成立即显示出 对紫外线的敏感度比预期高出约20倍 根据U单链RNA转录单位的大小。这是唯一的 表达对紫外线即刻敏感的已知基因 辐射。第二，延迟紫外光对U-SnRNA的抑制作用 转录需要大约1-2小时的辐射后细胞孵化和 紫外线剂量比同类产品所需的剂量低约十分之一 立即抑制水平，并且没有观察到任何其他RNA 物种。 既然这两个禁忌是独一无二的，那么就应该有一些独一无二的 这两者背后的机制都有有趣的特征 抑制的类型。我们的最终目标是确定 这两种类型的抑制。详细分析了其作用机理。 这两种抑制将需要复制它们的无细胞系统。 首先，生产这两类产品所需的基本要素 必须定义抑制，这是 现提交建议书。关于这两种抑制作用机制的一些模型 与现有的结果是一致的。致危重病变的原因 紫外线可能在DNA上，但远离U1基因区。两种选择 模特现在不能被排除在外。小剂量的紫外线可能会产生 对某一序列或分子的不成比例的损害，或 给定序列或分子中的少量紫外线损伤可能会导致 不成比例的功能丧失。然后，尽管很明显 目标尺寸的差异，可以想象紫外光诱导 DNA与另一个分子的交联性，很可能是蛋白质，或直接 对蛋白质的损伤，可能是这两种疾病中任何一种的关键损伤 禁忌。提出了一系列实验来检验这些 U1 RNA基因的假设，基于瞬时表达分析， 将U1 RNA基因注入非洲爪哇卵母细胞，转录 在分离的细胞核中，在无细胞提取液中转录。

We are studying some novel effects of UV radiation, a major environmental carcinogen and mutagen, in animal cells. UV light induces two unique and distinct types of inhibition of the synthesis of small nuclear RNA (snRNA) species U1, U2, U3, U4, and U5. (U1, U2 and U4 RNA, and possibly U5 RNA, each have essential functions.) U snRNA synthesis shows an immediate sensitivity to UV light that is about 20 times greater than that expected from the sizes of the U snRNA transcription units. These are the only known genes whose expression exhibits an immediate hypersensitivity to UV radiation. A second, delayed UV light-induced inhibition of U snRNA transcription requires about 1-2 hr of postirradiation cell incubation and UV doses that are about 10-fold lower than those needed for a comparable level of immediate inhibition, and has not been observed with any other RNA species. Since these two inhibitions are unique, there should be some unique and interesting features in the mechanism underlying each one of these two types of inhibition. Our ultimate goal is to determine the mechanisms of these two types of inhibition. Detailed analysis of the mechanisms of these two inhibitions will require cell-free systems that reproduce them. First, the essential elements needed to produce these two types of inhibition have to be defined, and that is the immediate goal of the present proposal. Some models for the mechanisms of these two inhibitions are compatible with the available results. The critical lesion induced by UV light may be on DNA, but away from the U1 gene region. Two alternative models cannot be rules out now. A small UV dose might produce a disproportionate amount of damage to a certain sequence or molecule, or a small amount of UV damage in a given sequence or molecule might result in a disproportionate loss of function. Then, in spite of the apparent discrepancy in target size, it is conceivable that UV light-induced crosslinking of DNA to another molecule, most likely a protein, or direct damage to a protein, might be the critical lesion in any of these two inhibitions. A sequence of experiments is proposed to test these hypotheses for U1 RNA genes, based on transient expression assays, intranuclear injection of U1 RNA genes into Xenopus oocytes, transcription in isolated nuclei, and transcription in cell-free extracts.