Dynactin complex is involved in a novel checkpoint to monitor cell wall synthesis in Saccharomyces cerevisiae.
Yoshikazu Ohya, Masaya Suzuki, Ryoji Igarashi, Takahiko Utsugi, Masashi Yukawa
Grad. Sch. of Frontier Science, University of Tokyo, Bldg. FSB-101, 5-1-5, Kashiwa, 277-8562, Japan
In the budding yeast, cell cycle progression is restrictively regulated and some events during cell cycle are regulated by the cell cycle checkpoints. Here we report that a novel checkpoint exists to couple cell wall remodeling with spindle formation. Surprisingly, fks1 mutants defective in 1,3-beta-glucan synthase activity arrested with post-replicative DNA but quite low level of Clb2p, and without forming bipolar spindles. We isolated a wac1 (wall-checkpoint defective) mutation that abolished this arrest caused the accumulation of Clb2p and CLB2 mRNA. Accordingly, wac1 leaded to formation of bipolar spindles despite glucan-synthesis perturbation, suggesting that Wac1p is required to achieve this checkpoint function through a transcriptional regulation of CLB2. Since the transcription factors consisting of Mcm1p-Fkh2p complex regulate the transcription of CLB2 in G2/M, we examined whether the cell wall checkpoint actually depends on regulating Fkh2p. Genetic and biochemical analyses indicated that CLB2 transcription is regulated through Fkh2p when the cell wall checkpoint is induced. Furthermore, we revealed that WAC1 is identical with ARP1 . Arp1p, Nip100p and Jnm1p, which are components of the dynactin complex, are all required to achieve the G2 arrest while keeping cells highly viable. These results indicate that the dynactin complex has a regulatory role in the novel checkpoint to monitor cell wall synthesis.
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