Study of cell morphogenesis that is coupled with cell division cycle

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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.