Mechanisms of formation and destruction of the contractile ring during cytokinesis

我们用不同的细胞分析了收缩环的形成机理。在裂变酵母细胞中，收缩环是由核分裂期间积聚在细胞内侧的f -肌动蛋白索形成的。在这个过程中，由f -肌动蛋白缆索组成的星形结构和从该结构延伸出来的导缆是很重要的。Cdcl2起引线延伸作用，Cdc15起F-actin电缆向引线融合作用。我们还分析了裂变酵母中Rho蛋白的功能，发现了一个新的g蛋白Rho3。Rho3定位于细胞膜。在Rho3或Cdc42的下游发现了一种新的formin家族蛋白For3。Rho3和For3同时控制肌动蛋白细胞骨架和微管，从而调节细胞的形状和细胞分裂的位置。cl4 （PAK）和Bni1 （formin）共同调控出芽酵母的septin环。f -肌动蛋白在这个过程中起着更重要的作用。在四膜虫中，二聚体EF1a捆绑f -肌动蛋白。Ca/钙调蛋白解离EF1a二聚体，从而抑制f -肌动蛋白的结合。四膜虫纤维蛋白以钙不敏感的方式结合和捆绑f -肌动蛋白。它局限于解理沟。我们发现，在海胆胚胎的第四分裂中，肌动蛋白在中心体附近的皮质中浓度较低，而在远离中心体的皮质中浓度较高，在形成沟槽的地方。分析了微管在爪蟾卵收缩环形成中的作用。微管毒素对微管的破坏不影响收缩环的收缩，但影响其形成。我们还发现，从两极发出的微管在解理沟下相互连接。我们通过分析解理沟周围的钙离子释放来测试钙离子在解理信号传导中发挥作用的可能性。在解理沟的前缘，既没有发现钙波，也没有发现小的钙释放，如钙泡或钙斑点。HeLa细胞中的rho激酶与丝蛋白a结合，因此，这些蛋白可能在收缩环中共定位。少

We analyzed mechanism of formation of the contractile ring using various cells. In fission yeast cells, the contractile ring is formed from F-actin cables which accumulate at the medial region of the cell during nuclear division. The aster-like structure consisting of F-actin cables and the leading cable which elongates from the structure are important in this process. Cdcl2 plays a role in elongation of the leading cable, while Cdc15 plays a role in the fusion of the F-actin cables to the leading cable. We also analyzed function of Rho proteins in fission yeast, and found a novel G-protein Rho3. Rho3 is localized to the cell membrane .It was found that a novel formin family protein For3 is present downstream of either Rho3 or Cdc42. Rho3 and For3 controls both actin cytoskeleton and microtubules, and thereby regulate shape of the cell and position of cytokinesis. Cla4(PAK) and Bni1 (formin) cooperatively function in regulation of the septin ring in budding yeast. F-actin plays an impo … More rtant role in this process. In Tetrahymena, dimeric EF1a bundles F-actin. Ca/calmodulin dissociates this EF1a dimer and thus inhibit the bundling of F-actin. Tetrahymena fimbrin binds and bundles F-actin in a Ca-insensitive manner. It is localized to the cleavage furrow. We found that actin is less concentrated in the cortex near the centrosome while concentrated in the cortex away from it, where the furrow is formed, in the fourth division in sea urchin embryos. Role of microtubules in formation of the contractile ring in Xenopus eggs was analyzed. Disruption of microtubules by microtubule poisons did not interfere with contraction of the contractile ring, but interfered with its formation. We also found that the microtubules emanated from the both poles link with each other beneath the cleavage furrow. We tested a possibility that Ca ions play a role in cleavage signaling by analyzing Ca release around the cleavage furrow. Neither Ca waves nor small Ca releases such as Ca puffs or Ca blips were found at the leading edge of the cleavage furrow. Rho-kinase in HeLa cells binds to filamin A. Thus, it is possible that these proteins co-localize in the contractile ring. Less