Fang Yuda, Hearn Stephen, Spector David L
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
Mol Biol Cell. 2004 Jun;15(6):2664-73. doi: 10.1091/mbc.e04-02-0100. Epub 2004 Mar 19.
The organization of the pre-mRNA splicing machinery has been extensively studied in mammalian and yeast cells and far less is known in living plant cells and different cell types of an intact organism. Here, we report on the expression, organization, and dynamics of pre-mRNA splicing factors (SR33, SR1/atSRp34, and atSRp30) under control of their endogenous promoters in Arabidopsis. Distinct tissue-specific expression patterns were observed, and differences in the distribution of these proteins within nuclei of different cell types were identified. These factors localized in a cell type-dependent speckled pattern as well as being diffusely distributed throughout the nucleoplasm. Electron microscopic analysis has revealed that these speckles correspond to interchromatin granule clusters. Time-lapse microscopy revealed that speckles move within a constrained nuclear space, and their organization is altered during the cell cycle. Fluorescence recovery after photobleaching analysis revealed a rapid exchange rate of splicing factors in nuclear speckles. The dynamic organization of plant speckles is closely related to the transcriptional activity of the cells. The organization and dynamic behavior of speckles in Arabidopsis cell nuclei provides significant insight into understanding the functional compartmentalization of the nucleus and its relationship to chromatin organization within various cell types of a single organism.
前体mRNA剪接机制的组织在哺乳动物和酵母细胞中已得到广泛研究，而在活植物细胞和完整生物体的不同细胞类型中了解较少。在此，我们报道了拟南芥中前体mRNA剪接因子（SR33、SR1/atSRp34和atSRp30）在其内源启动子控制下的表达、组织和动态变化。观察到了不同的组织特异性表达模式，并确定了这些蛋白质在不同细胞类型细胞核内分布的差异。这些因子以细胞类型依赖的斑点状模式定位，同时也在核质中呈弥散分布。电子显微镜分析表明，这些斑点对应于染色质间颗粒簇。延时显微镜显示斑点在有限的核空间内移动，并且它们的组织在细胞周期中发生改变。光漂白后荧光恢复分析显示核斑点中剪接因子的交换速率很快。植物斑点的动态组织与细胞的转录活性密切相关。拟南芥细胞核中斑点的组织和动态行为为理解单个生物体各种细胞类型中细胞核的功能区室化及其与染色质组织的关系提供了重要见解。
