Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., 142 20 Prague, Czech Republic.
Light Microscopy Core Facility, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., 142 20 Prague, Czech Republic.
Cells. 2021 Apr 8;10(4):848. doi: 10.3390/cells10040848.
Here, we provide evidence for the presence of Myosin phosphatase rho-interacting protein (MPRIP), an F-actin-binding protein, in the cell nucleus. The MPRIP protein binds to Phosphatidylinositol 4,5-bisphosphate (PIP2) and localizes to the nuclear speckles and nuclear lipid islets which are known to be involved in transcription. We identified MPRIP as a component of RNA Polymerase II/Nuclear Myosin 1 complex and showed that MPRIP forms phase-separated condensates which are able to bind nuclear F-actin fibers. Notably, the fibrous MPRIP preserves its liquid-like properties and reforms the spherical shaped condensates when F-actin is disassembled. Moreover, we show that the phase separation of MPRIP is driven by its long intrinsically disordered region at the C-terminus. We propose that the PIP2/MPRIP association might contribute to the regulation of RNAPII transcription via phase separation and nuclear actin polymerization.
在这里，我们提供了肌球蛋白磷酸酶 rho 相互作用蛋白（MPRIP）存在于细胞核中的证据，MPRIP 是一种 F-肌动蛋白结合蛋白。MPRIP 蛋白与磷脂酰肌醇 4,5-二磷酸（PIP2）结合，并定位于核斑点和核脂斑，这些斑点已知参与转录。我们将 MPRIP 鉴定为 RNA 聚合酶 II/核肌球蛋白 1 复合物的一个组成部分，并表明 MPRIP 形成相分离的凝聚物，能够结合核 F-肌动蛋白纤维。值得注意的是，纤维状的 MPRIP 保持其液态样特性，并在 F-肌动蛋白解聚时重新形成球形凝聚物。此外，我们表明 MPRIP 的相分离是由其 C 端的长固有无序区域驱动的。我们提出，PIP2/MPRIP 结合可能通过相分离和核肌动蛋白聚合来调节 RNAPII 转录。
