RNA PROCESSING AND NUCLEAR RIBONUCLEOPROTEIN

对真核生物基因调控机制的认识 表达对于更大的调控目标至关重要 这些过程在病变细胞状态下进行。 有效的控制 在转录后的核阶段， 被研究。 在此期间，前mRNA转录本被包装 与hnRNP和snRNP组分形成核糖核蛋白复合物 其成为剪接和聚腺苷酸化反应的底物; 然后它们作为成熟的mRNA从细胞核输出， 在细胞质中翻译。 A/B hnRNP蛋白与 在整个过程中，这些转录本与 它们与RNA共转录，并一直保持在一起， 核孔 有许多暗示性的证据表明，A/B hnRNP蛋白可能在RNA包装中起重要作用， 加工和出口，虽然明确的体内证据已经证明， 很难获得。 一个非常有利的制度已经建立， 黑腹果蝇，它将允许一个组合的 遗传学/细胞学/超微结构方法来研究 这些蛋白质在生物体内的功能。 利用最近 获得了在两个主要的A/B hnRNP中都具有无效突变的果蝇， 蛋白质基因，（以及当胚胎死亡时， 纯合子），将进行RNA转录、加工 和mRNA输出，因为蛋白质水平低于所需的水平， 正常功能。 这些测定将是超微结构（米勒染色质 扩散）、细胞学和表型。 苍蝇将被确定， 具有条件性表达的hnRNA蛋白基因， 可以在其他组织和发育阶段进行。 在这些蛋白质的大量可用生化数据的指导下， 表达特定突变蛋白的基因将被引入野生型中， 苍蝇 在此背景下，将测定它们是否可能 转显性效应对RNA加工和输出的影响， 与多烯上转录位点结合的特定模式 染色体 然后它们将被杂交到双突变果蝇中 并测定其拯救生存能力。 该组合 这种方法将是一种强有力的体内试验的作用， RNA识别、加工和输出领域，并将提供 A/B hnRNP蛋白在活体中的功能的关键测试 有机体

An understanding of the mechanisms and controls of eukaryotic gene expression is of critical importance to the larger goal of regulating these processess in diseased cell states. The controls that are operative on pre-messenger RNA at the post-transcriptional nuclear stage are being studied. During this period, pre-mRNA transcripts are packaged with hnRNP and snRNP components into a ribonucleoprotein complex which becomes the substrate for splicing and polyadenylation reactions; they are then exported from the nucleus as mature mRNAs for translation in the cytoplasm. The A/B hnRNP proteins are associated with these transcripts throughout the entire process--they bind to the RNA co-transcriptionally and they remain with it until after it transits the nuclear pore. There is much suggestive evidence that the A/B hnRNP proteins may play important roles in RNA packaging, processing and export, although definitive in vivo evidence has proven difficult to obtain. A very favorable system has been established in Drosophila melanogaster which will allow a combined genetic/cytological/ultrastructural approach to investigation of the function of these proteins in a living organism. Using recently obtained flies that have null mutations in both of the major A/B hnRNP protein genes, (and which are late embryonic lethals when homozygous), assays will be done of RNA transcription, processing and mRNA export as the protein levels fall below that required for normal function. These assays will be ultrastructural (Miller chromatin spreading), cytological and phenotypic. Flies will be established that have a conditionally expressed hnRNA protein gene so that these assays can be done in other tissues and developmental stages of interest. Guided by a wealth of available biochemical data on these proteins, genes expressing specific mutant proteins will be introduced into wild flies. In this background, they will be assayed for possible transdominant effects on RNA processing and export and for their specific patterns of binding to sites of transcription on polytene chromosomes. They will then be crossed into the double mutant flies and assayed for their ability to rescue viability. This combined approach will be a powerful in vivo test of the role of specific protein domains in RNA recognition, processing and export and will provide a critical test of the function of A/B hnRNP proteins in a living organism.