Small RNP Mediators of Gene Expression

描述（由申请人提供）：信使RNA生物发生的核步骤是由小核核糖核蛋白（snRNPs）编排的，snRNPs是两个剪接体和组蛋白mRNA 3'端加工机制的核心参与者。其他种类的snRNPs指导核仁核糖体rna （snoRNPs）或Cajal小体剪接体snRNAs （scaRNPs）的核苷酸修饰。一类新的微小RNPs， microRNPs，在细胞核中经历了早期的生物发生步骤，但在细胞质中起作用，调节mRNA靶标的翻译。snRNPs、scaRNPs和microRNPs的作用机制和生物发生将被研究，重点是利用哺乳动物细胞、非洲爪蟾卵母细胞、果蝇和酵母细胞进行潜在的分子相互作用。这些小的RNPs及其组成部分如何促进基因表达步骤的耦合是一个中心焦点，包括用于执行各种过程的共同组成部分之间的协同作用。对于框C/D scaRNPs，我们将阐明负责其Cajal体定位的信号和因素，这使得它们能够作用于剪接体snrna。我们将研究在果蝇普洛斯普洛斯pre-mRNA中使用主要剪接体（u2型）或次要剪接体（u12型）之间的选择。我们将完成RNA功能基团的分析，并阐明剪接体组分的相互作用，剪接体组分对于外显子连接上游新剪接的mRNA上称为外显子连接复合物（EJC）的多蛋白复合物沉积至关重要。我们将研究EJC核心组分（elF4AIII）的替代作用，我们已经发现它可以在功能上取代其酵母同源物Fall p。我们将确定在组蛋白前mRNA的3‘端切割中起作用的切割/多腺苷化因子CPSF的亚基，U7 snRNP如何招募切割/多腺苷化因子的亚基，以及结合U2 snRNP组分的保守RNA元件如何刺激组蛋白mRNA 3’端成熟。我们将研究诸如AGO2和FXR1等microRNP成分如何根据细胞生长条件在翻译中发挥抑制或刺激作用，以及microRNA初级转录本的加工是否发生在离散的核质位点上。这些研究将阐明各种人类疾病过程，这些过程可以追溯到小RNP生物发生、功能和关联的扰动。

DESCRIPTION (provided by applicant): The nuclear steps of messenger RNA biogenesis are orchestrated by small nuclear ribonucleoproteins (snRNPs), which are central players in the action of two spliceosomes and the histone mRNA 3'-end processing machinery. Other classes of snRNPs guide the nucleotide modification of ribosomal RNAs in the nucleolus (snoRNPs) or of spliceosomal snRNAs in Cajal bodies (scaRNPs). A novel class of tiny RNPs, microRNPs, undergoes early biogenesis steps in the nucleus but functions in the cytoplasm to regulate the translation of mRNA targets. The mechanisms of action and biogenesis of snRNPs, scaRNPs and microRNPs will be investigated with an emphasis on the underlying molecular interactions using mammalian cells, the Xenopus oocyte, as well as Drosophila and yeast cells. How these small RNPs and their constituents contribute to the coupling of steps in gene expression is a central focus, including the synergies between and common components used to execute various processes. For box C/D scaRNPs, we will elucidate the signals and factors responsible for their Cajal body localization, which enables their action on spliceosomal snRNAs. We will investigate alternative splicing involving a choice between use of the major (U2-type) or minor (U12-type) spliceosome in the Drosophila prospero pre-mRNA. We will complete analyses of RNA functional groups and elucidate interactions with spliceosome components that are essential for the deposition of a multiprotein complex called the exon junction complex (EJC) on newly spliced mRNA upstream of exon-exon junctions. We will investigate alternative roles of a core component of the EJC (elF4AIII), which we have discovered can functionally replace its yeast homolog, Fall p. We will identify the subunit of the cleavage/polyadenylation factor CPSF that acts in 3'-end cleavage of histone pre- mRNAs, how the U7 snRNP recruits a subset of cleavage/polyadenylation factors, and how a conserved RNA element that binds U2 snRNP components stimulates histone mRNA 3'-end maturation. We will investigate how microRNP components such as AGO2 and FXR1 play repressive versus stimulatory roles in translation depending on cell growth conditions, and whether the processing of microRNA primary transcripts occurs in discrete nucleoplasmic loci. These studies will illuminate a variety of human disease processes that can be traced to perturbations in small RNP biogenesis, functions and associations.