Visualization of actin filaments and monomers in somatic cell nuclei.
Visualization of actin filaments and monomers in somatic cell nuclei.
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DOI：
10.1091/mbc.e12-09-0685
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发表时间：
2013-04
影响因子：
3.3
通讯作者：
Mullins RD
中科院分区：
文献类型：
--
作者：
Belin BJ;Cimini BA;Blackburn EH;Mullins RD
荧光核肌动蛋白报告基因用于确定活体细胞中核肌动蛋白的分布并评估其潜在功能。他们揭示了活体细胞核中不同的单体和丝状肌动蛋白群体，并表明核肌动蛋白参与了 mRNA 加工和核质组织。除了长期研究其存在于细胞质中之外，肌动蛋白还存在于真核细胞的细胞核中。核肌动蛋白的功能和形式（单体、丝状或非规范寡聚体）受到激烈争论，其定位和动力学在很大程度上是未知的。为了确定活体细胞中核肌动蛋白的分布并评估其潜在功能，我们构建并验证了荧光核肌动蛋白探针。单体肌动蛋白探针集中在核斑点中，表明单体与 RNA 加工因子存在相互作用。丝状肌动蛋白探针可识别亚微米长度的离散结构，这些结构被排除在富含染色质的区域之外。在延时电影中，这些肌动蛋白丝结构表现出两种类型的迁移率之一：1) 扩散型，平均扩散系数为 0.06–0.08 μm2/s，或 (2) 亚扩散型，迁移系数为 0.015 μm2/s。单个细丝轨迹表现出颗粒在粘弹性网格内移动的特征。核肌动蛋白丝的小尺寸与微米级核内运输的作用不一致，它们的定位表明它们不直接参与基于染色质的过程。相反，我们的结果表明肌动蛋白丝形成核质中大型粘弹性结构的一部分，并且可能充当帮助组织核内容物的支架。
Fluorescent nuclear actin reporters are used to determine the distribution of nuclear actin in live somatic cells and evaluate its potential functions. They reveal distinct monomeric and filamentous actin populations in nuclei of live somatic cells and implicate nuclear actin in mRNA processing and organization of the nucleoplasm. In addition to its long-studied presence in the cytoplasm, actin is also found in the nuclei of eukaryotic cells. The function and form (monomer, filament, or noncanonical oligomer) of nuclear actin are hotly debated, and its localization and dynamics are largely unknown. To determine the distribution of nuclear actin in live somatic cells and evaluate its potential functions, we constructed and validated fluorescent nuclear actin probes. Monomeric actin probes concentrate in nuclear speckles, suggesting an interaction of monomers with RNA-processing factors. Filamentous actin probes recognize discrete structures with submicron lengths that are excluded from chromatin-rich regions. In time-lapse movies, these actin filament structures exhibit one of two types of mobility: 1) diffusive, with an average diffusion coefficient of 0.06–0.08 μm2/s, or (2) subdiffusive, with a mobility coefficient of 0.015 μm2/s. Individual filament trajectories exhibit features of particles moving within a viscoelastic mesh. The small size of nuclear actin filaments is inconsistent with a role in micron-scale intranuclear transport, and their localization suggests that they do not participate directly in chromatin-based processes. Our results instead suggest that actin filaments form part of a large, viscoelastic structure in the nucleoplasm and may act as scaffolds that help organize nuclear contents.