GTP-dependent formation of a ribonucleoprotein subcomplex required for ribosome biogenesis
GTP-dependent formation of a ribonucleoprotein subcomplex required for ribosome biogenesis
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DOI：
10.1016/j.jmb.2005.11.052
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发表时间：
2006-02-17
影响因子：
5.6
通讯作者：
Doudna, JA
中科院分区：
文献类型：
--
作者：
Karbstein, K;Doudna, JA
真核生物的核糖体生物发生涉及78种核糖体蛋白与4种核糖体rna的协调组装，由一系列反式作用因子介导，这些因子的具体功能在很大程度上尚不清楚。必需的GTPase Bms1，假定的内切酶Rcl1和必需的U3小核核RNA形成一个稳定的亚复合物，被认为控制40s核糖体亚基组装的早期步骤。在这里，我们对GTP依赖性亚复合物形成进行了完整的热力学分析，揭示了Rcl1， U3小核核RNA和GTP与Bms1结合的强热力学耦合，该耦合在GDP存在下被消除。结果表明，Rcl1通过促进GDP/GTP交换来激活Bms1，类似于核糖体促进翻译伸长因子EF-G内的核苷酸交换。这些和其他数据揭示了Bms1和参与翻译的gtpase亚群之间的热力学相似性，提供了部分核糖体组装机制可能是从翻译装置进化而来的证据。这种对核糖体前组装早期和重要步骤的定量描述，为阐明Bms1亚复合物与核糖体生物发生中涉及的其他因子之间的相互作用网络提供了一个框架。(c) 2005 Elsevier Ltd版权所有。
Ribosome biogenesis in eukaryotic organisms involves the coordinated assembly of 78 ribosomal proteins onto the four ribosomal RNAs, mediated by a host of trans-acting factors whose specific functions remain largely unknown. The essential GTPase Bms1, the putative endonuclease Rcl1 and the essential U3 small nucleolar RNA form a stable subcomplex thought to control an early step in the assembly of the 40 S ribosomal subunit. Here, we provide a complete thermodynamic analysis of GTP-dependent subcomplex formation, revealing strong thermodynamic coupling of Rcl1, U3 small nucleolar RNA and GTP binding to Bms1 that is eliminated in the presence of GDP. The results suggest that Rcl1 activates Bms1 by promoting GDP/GTP exchange, analogous to ribosome-promoted nucleotide exchange within translation elongation factor EF-G. These and other data unveil thermodynamic similarities between Bms1 and the subgroup of GTPases involved in translation, providing evidence that parts of the ribosome assembly machinery may have evolved from the translation apparatus. This quantitative description of an early and essential step in pre-ribosome assembly provides a framework for elucidating the network of interactions between the Bms1 subcomplex and additional factors involved in ribosome biogenesis. (c) 2005 Elsevier Ltd. All rights reserved.