Department of Integrated Genetics, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan.
J Cell Sci. 2012 Jan 1;125(Pt 1):166-75. doi: 10.1242/jcs.090837. Epub 2012 Jan 16.
The nucleus in eukaryotic cells is a highly organized and dynamic structure containing numerous subnuclear bodies. The morphological appearance of nuclear bodies seems to be a reflection of ongoing functions, such as DNA replication, transcription, repair, RNA processing and RNA transport. The integrator complex mediates processing of small nuclear RNA (snRNA), so it might play a role in nuclear body formation. Here, we show that the integrator complex is essential for integrity of the Cajal body. Depletion of INTS4, an integrator complex subunit, abrogated 3'-end processing of snRNA. A defect in this activity caused a significant accumulation of the Cajal body marker protein coilin in nucleoli. Some fractions of coilin still formed nucleoplasmic foci; however, they were free of other Cajal body components, such as survival of motor neuron protein (SMN), Sm proteins and snRNAs. SMN and Sm proteins formed striking cytoplasmic granules. These findings demonstrate that the integrator complex is essential for snRNA maturation and Cajal body homeostasis.
真核细胞的核是一个高度组织化和动态的结构，包含许多核内小体。核内小体的形态外观似乎反映了正在进行的功能，如 DNA 复制、转录、修复、RNA 加工和 RNA 运输。整合体复合物介导小核 RNA（snRNA）的加工，因此它可能在核小体形成中发挥作用。在这里，我们表明整合体复合物对于 Cajal 体的完整性是必不可少的。整合体复合物亚基INTS4 的耗竭消除了 snRNA 的 3'-末端加工。这种活性的缺陷导致 Cajal 体标记蛋白 coilin 在核仁中的大量积累。 coilin 的一些部分仍然形成核质焦点；然而，它们没有其他 Cajal 体成分，如运动神经元生存蛋白 (SMN)、Sm 蛋白和 snRNAs。SMN 和 Sm 蛋白形成明显的细胞质颗粒。这些发现表明整合体复合物对于 snRNA 成熟和 Cajal 体动态平衡是必不可少的。
