Modification of Sm small nuclear RNAs occurs in the nucleoplasmic Cajal body following import from the cytoplasm
Modification of Sm small nuclear RNAs occurs in the nucleoplasmic Cajal body following import from the cytoplasm
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DOI：
10.1093/emboj/cdg187
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发表时间：
2003-04-15
期刊：
影响因子：
11.4
通讯作者：
Kiss, T
中科院分区：
文献类型：
--
作者：
Jády, BE;Darzacq, X;Kiss, T
功能性剪接体小核 RNA (snRNA) 的生物发生包括许多内部核苷酸的转录后共价修饰。我们最近证明，RNA 聚合酶 II 合成的 Sm snRNA 中 2'-O-甲基化核苷酸和假尿苷的合成是由序列特异性指导 RNA 指导的。在这里，我们提供了支持 Sm snRNA 修饰发生在核质卡哈尔体 (CB) 中这一观点的证据，修饰引导 RNA 在此聚集。我们表明，当靶向 CB 时，Sm snRNA 的短片段会被正确且有效地修饰，但当这些相同的片段靶向核仁时则不会。我们还证明，U2 snRNA 的内部修饰仅在从细胞质中新组装的 Sm snRNP 进入核后发生。最后，我们证明 p80 线圈蛋白（CB 标记蛋白）不是 snRNA 修饰所必需的。在线圈蛋白敲除细胞中，Sm snRNA 及其修饰指导 RNA 共定位于残留的 CB 中，这些 CB 不会储存原纤维蛋白，也无法募集 U3 小核仁 RNA。
Biogenesis of functional spliceosomal small nuclear RNAs (snRNAs) includes the post-transcriptional covalent modification of numerous internal nucleotides. We have recently demonstrated that synthesis of 2'-O-methylated nucleotides and pseudouridines in the RNA polymerase II-synthesized Sm snRNAs is directed by sequence-specific guide RNAs. Here, we provide evidence supporting the notion that modification of Sm snRNAs occurs in nucleoplasmic Cajal bodies (CBs), where modification guide RNAs accumulate. We show that short fragments of Sm snRNAs are correctly and efficiently modified when targeted to CBs, but not when these same fragments are targeted to the nucleolus. We also demonstrate that internal modification of the U2 snRNA occurs exclusively after nuclear import of the newly assembled Sm snRNP from the cytoplasm. Finally, we show that p80 coilin, the CB marker protein, is not required for snRNA modification. In coilin knockout cells, Sm snRNAs and their modification guide RNAs colocalize in residual CBs, which do not stockpile fibrillarin and fail to recruit the U3 small nucleolar RNA.