Steady-state dynamics of Cajal body components in the Xenopus germinal vesicle.
Steady-state dynamics of Cajal body components in the Xenopus germinal vesicle.
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爪蟾生发囊泡中Cajal体成分的稳态动力学。
DOI：
10.1083/jcb.200212024
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发表时间：
2003-02-17
影响因子：
7.8
通讯作者：
Gall, Joseph G
中科院分区：
文献类型：
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作者：
Handwerger, Korie E;Murphy, Christine;Gall, Joseph G
卡哈尔体（CB）是进化上保守的核细胞器，含有许多参与RNA转录和加工的因子。有人建议，大分子复合物预组装或在CB内经历成熟，然后才在细胞核的其他地方发挥作用。大多数这样的CB功能模型预测CB和核质之间的分子连续流动，但很少有数据直接支持这一观点。我们使用荧光恢复后光漂白（FRAP）对分离的非洲爪蟾卵母细胞核，以测量三个荧光标记分子的核质和CB之间的稳态交换率：U 7小核RNA，卷曲蛋白，和TATA结合蛋白（TBP）。在核质中，三种分子的表观扩散系数范围为0.26 ~ 0.40 μm2 s-1。然而，在CB中，荧光恢复明显慢于在核质中，并且至少有三个动力学成分。CB内的回收率与漂白斑直径无关，不能归因于高CB粘度或密度。我们建议，结合到其他分子，并可能组装成更大的复合物的速率限制步骤的FRAP的U 7，卷曲蛋白，和TBP内CB。
Cajal bodies (CBs) are evolutionarily conserved nuclear organelles that contain many factors involved in the transcription and processing of RNA. It has been suggested that macromolecular complexes preassemble or undergo maturation within CBs before they function elsewhere in the nucleus. Most such models of CB function predict a continuous flow of molecules between CBs and the nucleoplasm, but there are few data that directly support this view. We used fluorescence recovery after photobleaching (FRAP) on isolated Xenopus oocyte nuclei to measure the steady-state exchange rate between the nucleoplasm and CBs of three fluorescently tagged molecules: U7 small nuclear RNA, coilin, and TATA-binding protein (TBP). In the nucleoplasm, the apparent diffusion coefficients for the three molecules ranged from 0.26 to 0.40 μm2 s−1. However, in CBs, fluorescence recovery was markedly slower than in the nucleoplasm, and there were at least three kinetic components. The recovery rate within CBs was independent of bleach spot diameter and could not be attributed to high CB viscosity or density. We propose that binding to other molecules and possibly assembly into larger complexes are the rate-limiting steps for FRAP of U7, coilin, and TBP inside CBs.