Role of Accessory Proteins P50/P55 in SnoRNP Biogenesis

辅助蛋白 P50/P55 在 SnoRNP 生物发生中的作用

• 批准号: 0215545
• 负责人: E Stuart Maxwell
• 金额: $ 40.54万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0215545&HistoricalAwards=false
• 关键词: Role; Accessory; Proteins; P50; P55

The small nucleolar RNAs (snoRNAs) play essential roles in eukaryotic ribosome biosynthesis. Critical snoRNA functions include directing cleavage of the pre-ribosomal RNA precursor and guiding the modification of specific nucleotides in the ribosomal RNAs. More than 100 snoRNAs have been identified in the nucleolus, thus establishing the snoRNAs as the largest class of small stable RNAs found in eukaryotic cells. Investigations have demonstrated that the box C/D and H/ACA snoRNAs exhibit evolutionarily conserved sequences and folded structures characteristic of each family. Each of these RNA motifs bind family-specific proteins to establish the snoRNA:protein (snoRNP) complex. Both the box C/D and H/ACA snoRNA motifs and their associated core proteins are required for snoRNA processing, snoRNP transport, and snoRNA-guided nucleotide modification of ribosomal RNAs. Most recently, two novel accessory proteins have been identified that are also essential for snoRNP synthesis. Accessory proteins p50 and p55 interact with the snoRNP core complex in the nucleoplasm and regulate snoRNP production. Despite their critical nature, nothing is yet known about how p50/p55 function in the synthesis of new snoRNP complexes. Therefore, the goals of this research are twofold. First, p50/p55's role in snoRNP biogenesis will be examined in vivo in the Xenopus oocyte nucleus. Microinjection experiments will determine the possible role of these accessory proteins for snoRNP assembly in the nucleoplasm as well as their potential function in transporting mature snoRNP complexes into the nucleolus. Second, structural studies will define the interactions of p50/p55 with the box C/D core snoRNP complex, providing mechanistic details of accessory protein function in regulating the snoRNP biosynthetic pathway. p50 and p55 are the first identified snoRNP accessory proteins essential for snoRNP biosynthesis. Defining their functional roles will provide fundamental insight into the snoRNA/snoRNP biosynthetic pathway. The involvement of p50/p55 in other nucleoplasmic events such as chromatin remodeling and RNA synthesis has suggested that p50 and p55 are multifunctional proteins and may serve as "molecular bridges" to coordinate various processes in the eukaryotic nucleus. Therefore, this research has the potential to impact our basic understanding of RNA metabolism in the eukaryotic nucleus and reveal new regulatory paradigms of gene expression.

小核仁 RNA (snoRNA) 在真核核糖体生物合成中发挥重要作用。 关键的 snoRNA 功能包括指导前核糖体 RNA 前体的裂解和指导核糖体 RNA 中特定核苷酸的修饰。 核仁中已鉴定出 100 多种 snoRNA，从而使 snoRNA 成为真核细胞中发现的最大一类小稳定 RNA。 研究表明，box C/D 和 H/ACA snoRNA 表现出每个家族的进化保守序列和折叠结构特征。 这些 RNA 基序中的每一个都结合家族特异性蛋白质以建立 snoRNA:蛋白质 (snoRNP) 复合物。 框 C/D 和 H/ACA snoRNA 基序及其相关核心蛋白都是 snoRNA 加工、snoRNP 运输和 snoRNA 引导的核糖体 RNA 核苷酸修饰所必需的。 最近，已经鉴定出两种新的辅助蛋白，它们对于 snoRNP 的合成也至关重要。 辅助蛋白 p50 和 p55 与核质中的 snoRNP 核心复合物相互作用并调节 snoRNP 的产生。尽管其性质至关重要，但关于 p50/p55 在新 snoRNP 复合物的合成中如何发挥作用尚不清楚。 因此，这项研究的目标是双重的。 首先，将在爪蟾卵母细胞核中体内检查 p50/p55 在 snoRNP 生物发生中的作用。 显微注射实验将确定这些辅助蛋白对于核质中 snoRNP 组装的可能作用，以及它们在将成熟 snoRNP 复合物转运到核仁中的潜在功能。 其次，结构研究将定义 p50/p55 与 box C/D 核心 snoRNP 复合物的相互作用，提供调节 snoRNP 生物合成途径的辅助蛋白功能的机制细节。 p50 和 p55 是第一个被鉴定的 snoRNP 生物合成必需的辅助蛋白。 定义它们的功能作用将为 snoRNA/snoRNP 生物合成途径提供基础见解。 p50/p55 参与其他核质事件，如染色质重塑和 RNA 合成，表明 p50 和 p55 是多功能蛋白质，可以作为“分子桥梁”来协调真核细胞核中的各种过程。 因此，这项研究有可能影响我们对真核细胞核中RNA代谢的基本理解，并揭示新的基因表达调控范式。