Anghileri P, Branduardi P, Sternieri F, Monti P, Visintin R, Bevilacqua A, Alberghina L, Martegani E, Baroni M D
Dipartimento di Fisiologia e Biochimica Generali, Università degli Studi di Milano, Via Celoria 26, Milan, 20133, Italy.
Exp Cell Res. 1999 Aug 1;250(2):510-23. doi: 10.1006/excr.1999.4531.
Cell cycle progression of somatic cells depends on net mass accumulation. In Saccharomyces cerevisiae the cAMP-dependent kinases (PKAs) promote cytoplasmic growth and modulate the growth-regulated mechanism triggering the begin of DNA synthesis. By altering the cAMP signal in budding yeast cells we show here that mitotic events can also depend on growth. In fact, the hyperactivation of PKAs permanently inhibited both anaphase and exit from mitosis when cell growth was repressed. In S. cerevisiae the anaphase promoting complex (APC) triggers entry into anaphase by mediating the degradation of Pds1p. The cAMP pathway activation was lethal together with a partial impairment of the Cdc16p APC subunit, causing a preanaphase arrest, and conversely low PKA activity suppressed the lethality of cdc16-1 cells. Deregulated PKAs partially prevented the decrease of Pds1p intracellular levels concomitantly with the anaphase inhibition, and the PKA-dependent preanaphase arrest could be suppressed in pds1(-) cells. Thus, the cAMP pathway and APC functionally interact in S. cerevisiae and Pds1p is required for the cAMP-mediated inhibition of chromosome separation. Exit from mitosis requires APC, Cdc15p, and the polo-like Cdc5p kinase. PKA hyperactivation and a cdc15 mutation were synthetically lethal and brought to a telophase arrest. Finally, a low cAMP signal allowed cell division at a small cell size and suppressed the lethality of cdc15-2 or cdc5-1 cells. We propose that mitosis progression and the M/G1 phase transition specifically depend on cell growth through a mechanism modulated by PKAs and interacting with the APC/CDC15/CDC5 mitotic system. A possible functional antagonism between PKAs and the mitosis promoting factor is also discussed.
体细胞的细胞周期进程取决于净质量积累。在酿酒酵母中，依赖于环磷酸腺苷（cAMP）的激酶（PKA）促进细胞质生长，并调节触发DNA合成起始的生长调节机制。通过改变出芽酵母细胞中的cAMP信号，我们在此表明有丝分裂事件也可能依赖于生长。事实上，当细胞生长受到抑制时，PKA的过度激活会永久性地抑制后期以及有丝分裂的退出。在酿酒酵母中，后期促进复合物（APC）通过介导Pds1p的降解来触发进入后期。cAMP途径的激活与Cdc16p APC亚基的部分损伤一起是致命的，导致前期阻滞，相反，低PKA活性抑制了cdc16 - 1细胞的致死性。失调的PKA部分阻止了Pds1p细胞内水平随着后期抑制而降低，并且PKA依赖性的前期阻滞在pds1（-）细胞中可以被抑制。因此，cAMP途径和APC在酿酒酵母中功能上相互作用，并且Pds1p是cAMP介导的染色体分离抑制所必需的。有丝分裂的退出需要APC、Cdc15p和类polo样Cdc5p激酶。PKA过度激活和cdc15突变是合成致死的，并导致末期阻滞。最后，低cAMP信号允许在小细胞大小下进行细胞分裂，并抑制cdc15 - 2或cdc5 - 1细胞的致死性。我们提出，有丝分裂进程和M/G1期转换特别依赖于细胞生长，其机制由PKA调节并与APC/CDC15/CDC5有丝分裂系统相互作用。还讨论了PKA与有丝分裂促进因子之间可能的功能拮抗作用。
