Ongoing U snRNP biogenesis is required for the integrity of Cajal bodies
Ongoing U snRNP biogenesis is required for the integrity of Cajal bodies
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DOI：
10.1091/mbc.e06-03-0247
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发表时间：
2006-07-01
影响因子：
3.3
通讯作者：
Luehrmann, Reinhard
中科院分区：
文献类型：
--
作者：
Lemm, Ira;Girard, Cyrille;Luehrmann, Reinhard
Cajal小体（CB）参与剪接体U小核核糖核蛋白（U snRNP）生物发生的核相。在这里，我们已经调查了CB标记蛋白coilin，U snRNP，和蛋白质存在于C/D盒小核仁（sno）RNP在细胞中耗尽hTGS 1，SMN，或PHAX敲除这三种蛋白质中的任何一种的RNAi干扰U snRNP成熟之前，U snRNA Sm核心重新进入细胞核。引人注目的是，CB在hTGS 1、SMN或PHAX不存在的情况下丢失，并且卷曲蛋白分散在核质中成许多小的病灶。这表明典型CB的完整性依赖于正在进行的U snRNP生物发生。在缺乏hTGS 1、SMN或PHAX的细胞中，剪接体U snRNP在核灶中未显示出可检测的浓度，并且不与卷曲蛋白共定位。相反，C/D盒snORNP组分在抑制U snRNP成熟后浓缩到与卷曲蛋白部分共定位的核灶中。我们通过siRNA介导的耗竭证明，卷曲蛋白是U snRNP缩合所需的，但不是C/D盒snoRNP组分，进入核质灶，也是将这些因子合并成典型的CB。总之，我们的数据表明，CB有一个模块化的结构与不同的域spliceosomal U snRNP和snoRNP。
Cajal bodies (CBs) have been implicated in the nuclear phase of the biogenesis of spliceosomal U small nuclear ribonucleoproteins (U snRNPs). Here, we have investigated the distribution of the CB marker protein coilin, U snRNPs, and proteins present in C/D box small nucleolar (sno)RNPs in cells depleted of hTGS1, SMN, or PHAX Knockdown of any of these three proteins by RNAi interferes with U snRNP maturation before the reentry of U snRNA Sm cores into the nucleus. Strikingly, CBs are lost in the absence of hTGS1, SMN, or PHAX and coilin is dispersed in the nucleoplasm into numerous small foci. This indicates that the integrity of canonical CBs is dependent on ongoing U snRNP biogenesis. Spliceosomal U snRNPs show no detectable concentration in nuclear foci and do not colocalize with coilin in cells lacking hTGS1, SMN, or PHAX In contrast, C/D box snoRNP components concentrate into nuclear foci that partially colocalize with coilin after inhibition of U snRNP maturation. We demonstrate by siRNA-mediated depletion that coilin is required for the condensation of U snRNPs, but not C/D box snoRNP components, into nucleoplasmic foci, and also for merging these factors into canonical CBs. Altogether, our data suggest that CBs have a modular structure with distinct domains for spliceosomal U snRNPs and snoRNPs.