Study of cell morphogenesis that is coupled with cell division cycle

细胞增殖过程中细胞周期事件的协调部分是通过监测系统实现的。在出芽酵母中，细胞周期进程受到严格调控，细胞周期中的一些事件由监测DNA损伤、DNA复制、纺锤体完整性、纺锤体定位和细胞形态发生的检查点调控。目前还不清楚是否所有检查站的控制都已被确认。我们发现存在一个新的检查点，将细胞壁重塑与纺锤体形成结合起来。1,3-β-葡聚糖合成酶活性缺陷的FKSL突变体未能形成成熟芽。令人惊讶的是，这些细胞被复制后的DNA捕获，但C1b2p的水平相当低，而且没有形成双极纺锤体。我们报道了wadi（壁检查点缺陷）突变，该突变消除了这种阻滞，导致C1b2p和CLB2 mRNA的积累，并导致双极纺锤体的形成，尽管葡聚糖合成受到干扰。这些结果表明存在一种新的检查点机制来协调进入有丝分裂，并表明wac1p需要通过CLB2的转录调控来实现这种检查点功能。此外，我们发现WACI与ARP1（肌动蛋白相关蛋白）相同。Arp1p、Nip100p和Jnm1p是dynactin复合体的组成部分，它们是实现G2阻滞和保持细胞高存活率所必需的。这些结果表明，dynactin复合物在监测细胞壁合成的新检查点中具有调节作用。

The coordination of cell cycle events during cell proliferation is attained, in part, through surveillance systems. In the budding yeast Saccharomyces cerevisiae, cell cycle progression is restrictively regulated and some events during cell cycle are regulated by the checkpoints monitoring DNA damage, DNA replication, integrity of the spindle, spindle positioning and cell morphogenesis. It still remained unclear whether all of the checkpoint controls have been identified.We found that a novel checkpoint exists to couple cell wall remodeling with spindle formation. fksl mutants defective in 1,3-β-glucan synthase activity failed to form a mature bud. Surprisingly, these cells arrested with post-replicative DNA but quite low level of C1b2p, and without forming bipolar spindles. We reported that wadi (wall-checkpoint defective) mutation that abolished this arrest caused the accumulation of C1b2p and CLB2 mRNA and leaded to formation of bipolar spindles despite glucan-synthesis perturbation. These results indicate the existence of a novel checkpoint mechanism to coordinate entry into mitosis, and suggest that Wac1 p is required to achieve this checkpoint function through a transcriptional regulation of CLB2. Furthermore, we revealed that WACI was identical with ARP1 (actin-related protein). Arp1p, Nip100p and Jnm1p, which are components of the dynactin complex, are required to achieve the G2 arrest while keeping cells highly viable. These results indicate that the dynactin complex have a regulatory role in the novel checkpoint to monitor cell wall synthesis.