European Molecular Biology Laboratory; Heidelberg, Germany.
Nucleus. 2013 Jan-Feb;4(1):14-7. doi: 10.4161/nucl.22961. Epub 2012 Dec 4.
The transitions between the successive cell cycle stages depend on reversible protein phosphorylation events. The phosphorylation state of every protein within a cell is strictly determined by spatiotemporally controlled kinase and phosphatase activities. Nuclear disassembly and reassembly during open mitosis in higher eukaryotic cells is one such process that is tightly regulated by the reversible phosphorylation of key proteins. However, little is known about the regulation of these mitotic events. In particular, although kinase function during entry into mitosis is better studied, very little is known about how proteins are dephosphorylated to allow nuclear reformation at the end of mitosis. We have identified LEM‑4, a conserved protein of the nuclear envelope, as an essential coordinator of kinase and phosphatase activities during mitotic exit. Inhibition of VRK‑1 kinase and promotion of a PP2A phosphatase complex by LEM‑4 tightly regulate the phosphorylation state of BAF, an essential player of nuclear reformation at the end of mitosis. Here I offer extended comments on the contribution of LEM‑4 in the regulation of protein phosphorylation and nuclear reformation.
细胞周期各阶段的转变依赖于蛋白质可逆磷酸化事件。细胞内每种蛋白质的磷酸化状态严格取决于时空控制的激酶和磷酸酶活性。高等真核细胞有丝分裂中核的解体和重新组装就是这样一个过程，它受到关键蛋白可逆磷酸化的严格调控。然而，这些有丝分裂事件的调控机制知之甚少。特别是，尽管有丝分裂进入期的激酶功能研究得更好，但对于有丝分裂末期如何去磷酸化以允许核重建知之甚少。我们已经确定核膜上的保守蛋白 LEM-4 是有丝分裂退出过程中激酶和磷酸酶活性的重要协调蛋白。LEM-4 抑制 VRK-1 激酶并促进 PP2A 磷酸酶复合物，可紧密调节 BAF 的磷酸化状态，BAF 是有丝分裂末期核重建的必要参与者。在这里，我对 LEM-4 在蛋白质磷酸化和核重建调控中的作用提供了扩展评论。
