Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden.
Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden.
Int Rev Cell Mol Biol. 2014;311:183-230. doi: 10.1016/B978-0-12-800179-0.00004-0.
In the eukaryotic cell nucleus, actin and myosin are emerging as essential regulators of nuclear function. At gene level, they regulate chromatin and modulate RNA polymerase transcription, and at the RNA level, they are involved in the metabolism of ribonucleoprotein complexes. Furthermore, actin and myosin are involved in maintaining the structure of cell nucleus by mediating chromatin movement and by interacting with components of the nuclear lamina. This plethora of functions is now supported by evidence that nuclear actin polymerizes just like the cytoplasmic actin fraction. Based on these considerations, we now hypothesize that the nuclear myosin forms function as actin-based motors. In this chapter, our goal is to start from the knowledge acquired in the cytoplasmic field to explore how nuclear myosin functions in gene transcription. One of the pressing issues discussed here is whether nuclear myosin produces local tension or functions as transporters. Based on two current models reported in the literature, we discuss the topology of the actin-based nuclear myosin 1 motor and how it is believed to facilitate propulsion of the RNA polymerase machinery while maintaining chromatin that is compatible with transcription. These mechanisms will be placed in the context of cell cycle progression.
在真核细胞核中，肌动蛋白和肌球蛋白正在成为核功能的重要调节因子。在基因水平上，它们调节染色质并调节 RNA 聚合酶转录，在 RNA 水平上，它们参与核糖核蛋白复合物的代谢。此外，肌动蛋白和肌球蛋白通过介导染色质运动和与核纤层成分相互作用，参与维持细胞核的结构。现在有证据表明，核肌动蛋白与细胞质肌动蛋白部分一样聚合，这为众多功能提供了支持。基于这些考虑，我们现在假设核肌球蛋白的功能类似于基于肌动蛋白的马达。在本章中，我们的目标是从细胞质领域获得的知识出发，探讨核肌球蛋白如何在基因转录中发挥作用。这里讨论的一个紧迫问题是，核肌球蛋白是否产生局部张力或作为转运蛋白发挥作用。基于文献中报道的两个当前模型，我们讨论了基于肌动蛋白的核肌球蛋白 1 马达的拓扑结构，以及它如何被认为有助于推进 RNA 聚合酶机械，同时保持与转录兼容的染色质。这些机制将被置于细胞周期进展的背景下。
