Nonhierarchical ribonucleoprotein assembly suggests a strain-propagation model for protein-facilitated RNA folding.
Nonhierarchical ribonucleoprotein assembly suggests a strain-propagation model for protein-facilitated RNA folding.
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DOI：
10.1021/bi100267g
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发表时间：
2010-07-06
期刊：
影响因子：
2.9
通讯作者：
Weeks, Kevin M.
中科院分区：
文献类型：
--
作者：
Duncan, Caia D. S.;Weeks, Kevin M.
蛋白质在细胞核糖核蛋白（RNP）中起着多种关键作用，包括促进活性RNA构象的形成和稳定。然而，将大RNA转化为活性RNP所需的构象变化已被证明难以完全表征。在这里，我们使用高分辨率的方法来监测本地核苷酸的灵活性和溶剂的可及性几乎所有的核苷酸在bI3组I内含子RNP在四个装配状态：游离RNA，成熟酶结合的RNA，Mrs1结合的RNA，和完整的六组分holocomplex。游离RNA相对于剪接所需的二级结构错误折叠。成熟酶和Mrs1蛋白各自稳定远程三级相互作用，但单独的蛋白质都不诱导折叠成功能性二级结构。相比之下，同时结合两种蛋白质的结果在RNA中的大的二级结构重排，并产生了催化活性组I内含子结构。因此，bI3 RNP的RNA组分的二级和三级折叠不是独立的：RNA折叠是强烈非分级的。这些结果强调，蛋白质介导的RNA三级相互作用的稳定作用可以将二级结构拉成能量上不利但功能性的构象，并强调促进蛋白在RNP组装中的新作用。
Proteins play diverse and critical roles in cellular ribonucleoproteins (RNPs) including promoting formation of and stabilizing active RNA conformations. Yet, the conformational changes required to convert large RNAs into an active RNPs have proven difficult to characterize fully. Here we use high-resolution approaches to monitor both local nucleotide flexibility and solvent accessibility for nearly all nucleotides in the bI3 group I intron RNP in four assembly states: the free RNA, maturase-bound RNA, Mrs1-bound RNA, and the complete six-component holocomplex. The free RNA is misfolded relative to the secondary structure required for splicing. The maturase and Mrs1 proteins each stabilized long-range tertiary interactions but neither protein alone induced folding into the functional secondary structure. In contrast, simultaneous binding by both proteins results in large secondary structure rearrangements in the RNA and yielded the catalytically active group I intron structure. Secondary and tertiary folding of the RNA component of the bI3 RNP are thus not independent: RNA folding is strongly non-hierarchical. These results emphasize that protein-mediated stabilization of RNA tertiary interactions functions to pull the secondary structure into an energetically disfavored, but functional, conformation and emphasize a new role for facilitator proteins in RNP assembly.
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