UV-INDUCED INHIBITION OF SMALL NUCLEAR RNA SYNTHESIS

我们正在研究紫外线辐射的一些新效应， 致癌物和诱变剂。 紫外线诱导两个独特的， 抑制小核RNA（snRNA）合成的不同类型 种U1、U2、U3、U4和U 5。 (U1 U2和U4 RNA，可能还有U 5 RNA， 每个人都有自己的基本功能）。 U snRNA合成显示， 对紫外线的敏感性比预期高出约20倍 从U snRNA转录单位的大小。 这些是唯一的 其表达表现出对UV的速发型超敏性的已知基因 辐射 第二，延迟的UV光诱导的U snRNA抑制 转录需要约1-2小时的辐射后细胞孵育， 紫外线剂量比类似的辐射所需的剂量低约10倍。 立即抑制的水平，并没有观察到与任何其他RNA 物种 由于这两种抑制是独特的，应该有一些独特的， 这两个机制的有趣特征 抑制的类型。 我们的最终目标是确定 这两种抑制。 详细分析了 这两种抑制需要无细胞系统来复制它们。 首先，生产这两类产品所需的基本要素 必须定义抑制，这是我们的直接目标。 目前的提案。 这两种抑制机制的一些模型 与现有结果一致。 诱发的严重损伤 紫外线可能在DNA上，但远离U1基因区域。 两个备选 现在不能排除模型。 少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UV损伤可能导致 不成比例的功能丧失。 尽管表面上 目标尺寸的差异，可以想象，UV光诱导的 DNA与另一个分子的交联，最有可能是蛋白质，或直接 蛋白质的损伤，可能是这两种疾病中任何一种的关键病变， 抑制 一系列的实验提出来测试这些 基于瞬时表达测定的U1 RNA基因的假设， 非洲爪蟾卵母细胞核内注射U1 RNA基因，转录 在分离的细胞核中，以及在无细胞提取物中的转录。

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.