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首页> 外文期刊>Journal of Molecular Biology >An unusual chemical reactivity of Sm site adenosines strongly correlates with proper assembly of core U snRNP particles.
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An unusual chemical reactivity of Sm site adenosines strongly correlates with proper assembly of core U snRNP particles.

机译：Sm位腺苷的异常化学反应性与核心U snRNP颗粒的正确组装密切相关。

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摘要

The small nuclear ribonucleoprotein particles (snRNP) U1, U2, U4, and U5 contain a common set of eight Sm proteins that bind to the conserved single-stranded 5'-PuAU3-6GPu-3' (Sm binding site) region of their constituent U snRNA (small nuclear RNA), forming the Sm core RNP. Using native and in vitro reconstituted U1 snRNPs, accessibility of the RNA within the Sm core RNP to chemical structure probes was analyzed. Hydroxyl radical footprinting of in vitro reconstituted U1 snRNP demonstrated that riboses within a large continuous RNA region, including the Sm binding site, were protected. This protection was dependent on the binding of the Sm proteins. In contrast with the riboses, the phosphate groups within the Sm core site were accessible to modifying reagents. The invariant adenosine residue at the 5' end, as well as an adenosine two nucleotides downstream of the Sm binding site, showed an unexpected reactivity with dimethyl sulfate. This novel reactivity could be attributed to N7-methylation of the adenosine and was not observed in naked RNA, indicating that it is an intrinsic property of the RNA- protein interactions within the Sm core RNP. Further, this reactivity was observed concomitantly with formation of the Sm subcore intermediate during Sm core RNP assembly. As the Sm subcore can be viewed as the commitment complex in this assembly pathway, these results suggest that the peculiar reactivity of the Sm site adenosine bases may be diagnostic for proper assembly of the Sm core RNP. Consistent with this idea, a strong correlation was found between the unusual N7-A methylation sensitivity of the Sm core RNP and its ability to be imported into the nucleus of Xenopus laevis oocytes. Copyright 1999 Academic Press.
机译：小核糖核蛋白颗粒（snRNP）U1，U2，U4和U5包含一组共同的八个Sm蛋白，它们与它们组成的保守单链5'-PuAU3-6GPu-3'（Sm结合位点）区域结合U snRNA（小核RNA），形成Sm核心RNP。使用天然和体外重构的U1 snRNP，分析了Sm核心RNP中RNA的化学结构探针可及性。体外重建的U1 snRNP的羟基自由基足迹表明，大连续RNA区域（包括Sm结合位点）内的核糖受到保护。这种保护取决于Sm蛋白的结合。与核糖相反，修饰试剂可接近Sm核心位点内的磷酸基团。在5'端不变的腺苷残基，以及在Sm结合位点下游两个核苷酸的腺苷，显示出与硫酸二甲酯的出乎意料的反应性。这种新的反应性可能归因于腺苷的N7-甲基化，而在裸露的RNA中未观察到，表明它是Sm核心RNP中RNA-蛋白质相互作用的固有特性。此外，在Sm核RNP组装过程中伴随观察到该反应性与Sm亚核中间体的形成。由于Sm子核可被视为该组装途径中的参与复合物，因此这些结果表明Sm部位腺苷碱基的特殊反应性可诊断Sm核RNP的正确组装。与此想法相一致，在Sm核心RNP异常的N7-A甲基化敏感性与其被导入非洲爪蟾卵母细胞核的能力之间发现了强烈的相关性。版权所有1999，学术出版社。

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