Temasek Life Sciences Laboratory, The National University of Singapore, 1 Research Link, Singapore 117604, Singapore.
Curr Biol. 2011 Mar 22;21(6):467-72. doi: 10.1016/j.cub.2011.01.059. Epub 2011 Mar 3.
Correct positioning of the cell division machinery is crucial for genomic stability and cell fate determination. The fission yeast Schizosaccharomyces pombe, like animal cells, divides using an actomyosin ring and is an attractive model to study eukaryotic cytokinesis. In S. pombe, positioning of the actomyosin ring depends on the anillin-related protein Mid1p. Mid1p arrives first at the medial cortex and recruits actomyosin ring components to node-like structures, although how this is achieved is unknown. Here we show that the IQGAP-related protein Rng2p, an essential component of the actomyosin ring, is a key element downstream of Mid1p. Rng2p physically interacts with Mid1p and is required for the organization of other actomyosin ring components into cortical nodes. Failure of localization of Rng2p to the nodes prevents medial retention of Mid1p and leads to actomyosin ring assembly in a node-independent manner at nonmedial locations. We conclude that Mid1p recruits Rng2p to cortical nodes at the division site and that Rng2p, in turn, recruits other components of the actomyosin ring to cortical nodes, thereby ensuring correct placement of the division site.
细胞分裂机制的正确定位对于基因组稳定性和细胞命运决定至关重要。裂殖酵母 Schizosaccharomyces pombe 与动物细胞一样，使用肌动球蛋白环进行分裂，是研究真核细胞胞质分裂的理想模型。在 S. pombe 中，肌动球蛋白环的定位取决于与肌球蛋白相关的蛋白 Mid1p。Mid1p 首先到达中皮层，并将肌动球蛋白环成分募集到类似节点的结构中，尽管这是如何实现的尚不清楚。在这里，我们表明 IQGAP 相关蛋白 Rng2p 是肌动球蛋白环的必需组成部分，是 Mid1p 的关键下游元件。Rng2p 与 Mid1p 相互作用，并需要将其他肌动球蛋白环成分组织成皮质节点。Rng2p 不能定位到节点会阻止 Mid1p 保留在中皮层，导致肌动球蛋白环在非中皮层位置以不依赖节点的方式组装。我们得出结论，Mid1p 将 Rng2p 招募到分裂位点的皮质节点，而 Rng2p 反过来又将肌动球蛋白环的其他成分招募到皮质节点，从而确保正确放置分裂位点。
