INTERDEPENDENCE OF YEAST RIBOSOME ASSEMBLY FACTORS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 Ytm1、Nop7和Erb1是组装60S核糖体亚基所必需的、保守的核仁蛋白。这三种蛋白质中的每一种都依赖于另一种蛋白质组装成前乳糖体并与其稳定地结合。在没有它们的情况下，27SA3前-rRNA到27SB前-rRNA的处理被阻止。Nop7的中心结构域与Erb1保守的氨基末端中间部分之间的相互作用是它们被招募到前rRNPs中所必需的。然后Ytm1的WD40基序与Erb1氨基末端结合到Nop7结合部位。与这些相互作用结构域一致，只包含这些相互作用结构域的截短Ytm1或Erb1结构的表达使蛋白质能够相互结合，组装成前乳糖体，并对核糖体的生物发生造成显性的负面影响。在这些显性-负截断中，Ytm1保守的氨基末端的一半或Erb1的C末端的保守的WD40基序的功能是什么？ Erb1还可能在细胞的生长和增殖中发挥作用；Erb1的过表达干扰了有丝分裂染色体的分离。Erb1是如何参与这一途径的？ 为了解决这些问题，我们正在进行全基因组双杂交筛选，使用Ytm1的氨基末端一半，Erb1的C末端一半和全长Erb1。Erb1和Ytm1的这些部分与组装核糖体中的其他分子的相互作用可能是建立适当的核糖体生物发生动力学的关键。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ytm1, Nop7, and Erb1 are essential, conserved nucleolar proteins necessary for assembly of 60S ribosomal subunits. Each of these three proteins is dependent on the other for their assembly into and stable association with preribosomes. In their absence, processing of 27SA3 pre-rRNA to 27SB pre-rRNA is blocked. Interaction between the central domain of Nop7 with the conserved amino-terminal middle of Erb1 is required for their recruitment into pre-rRNPs. The WD40 motif of Ytm1 then binds to Erb1 amino-terminal to the Nop7 binding site. Consistent with these domains of interaction, expression of truncated Ytm1 or Erb1 constructs containing only these interaction domains enables the proteins to associate with each other, assemble into preribosomes, and cause a dominant negative effect on ribosome biogenesis. What are the functions of the conserved amino-terminal half of Ytm1 or the conserved WD40 motif in the C-terminal half of Erb1, which are missing in these dominant-negative truncations? Erb1 also may function in cell growth and proliferation; overexpression of Erb1 interferes with mitotic chromosome segregation. How does Erb1 participate in this pathway? To address these questions, we are carrying out genome-wide two-hybrid screens using the amino-terminal half of Ytm1, the C-terminal half of Erb1 and full-length Erb1. Interactions of these portions of Erb1 and Ytm1 with other molecules in assembling ribosomes may be critical to establish proper dynamics of ribosome biogenesis.