Fission yeast IQGAP maintains F-actin-independent localization of myosin-II in the contractile ring.
Fission yeast IQGAP maintains F-actin-independent localization of myosin-II in the contractile ring.
复制标题
裂殖酵母 IQGAP 维持肌球蛋白-II 在收缩环中的 F-肌动蛋白独立定位。
作者：
Takaine;M.;Numata;O.;and Nakano;K.
在许多真核细胞的胞质分裂过程中，肌球蛋白-II以肌动蛋白细丝(F-肌动蛋白)的形式集中在赤道皮质，并被认为产生将细胞一分为二的力量，这被称为收缩环(CR)假说。一些证据表明，肌球蛋白-II是独立于F-肌动蛋白招募的，并与赤道F-肌动蛋白特异性地相互作用。这些机制的分子细节仍不清楚。我们利用裂殖酵母研究了肌球蛋白-II的定位调控。通过同时观察F-肌动蛋白和肌球蛋白，我们证明了CR肌球蛋白-II是由F-肌动蛋白依赖和非依赖部分组成的。在没有F-肌动蛋白的情况下，F-肌动蛋白非依赖性部分显示为皮质点。IQGAP RNG2是CR不可缺少的元件，与肌球蛋白-II的F-肌动蛋白非依赖性组分的维持有关，而苯胺素MID1是组装所必需的，但不是维持该组分所必需的。在therng2突变体的CR中，肌球蛋白-II浓度较低、不稳定且不均匀，这往往导致胞质分裂失败。这些结果表明，RNG2独立于F-肌动蛋白，将肌球蛋白-II沿着CR连接到皮质，以提供足够的浓度。肌球蛋白-II的强大定位将确保细胞质分裂的成功。
During cytokinesis in many eukaryotic cells, myosin‐II concentrates at the equatorial cortex with actin filaments (F‐actin) and is supposed to generate forces to divide the cell into two, which is called the contractile ring (CR) hypothesis. Several lines of evidence indicate that the myosin‐II is recruited independently of F‐actin and interacts specifically with the equatorial F‐actin. Molecular details of these mechanisms are still unknown. We used the fission yeastSchizosaccharomyces pombeto investigate the regulation of myosin‐II localization. We demonstrate that the CR myosin‐II was composed of F‐actin‐dependent and ‐independent fractions by simultaneously observing F‐actin and myosin. The F‐actin‐independent fraction was visualized as cortical dots in the absence of F‐actin. IQGAP Rng2, an indispensable element of CR, was implicated in maintenance of the F‐actin‐independent fraction of myosin‐II, whereas anillin Mid1 was required for assembly but not for maintenance of the fraction. In the CR of therng2mutant, myosin‐II was less concentrated, unstable, and nonhomogeneous, which often resulted in cytokinesis failure. These results suggest that Rng2 tethers myosin‐II to the cortex along the CR independently of F‐actin to provide a sufficient concentration. The robust localization of myosin‐II would ensure successful cytokinesis.