Suppression of Scant Identifies Endos as a Substrate of Greatwall Kinase and a Negative Regulator of Protein Phosphatase 2A in Mitosis
Suppression of Scant Identifies Endos as a Substrate of Greatwall Kinase and a Negative Regulator of Protein Phosphatase 2A in Mitosis
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DOI：
10.1371/journal.pgen.1002225
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发表时间：
2011-08-01
期刊：
影响因子：
4.5
通讯作者：
Glover, David M.
中科院分区：
文献类型：
--
作者：
Rangone, Helene;Wegel, Eva;Glover, David M.
蛋白磷酸酶2A（PP 2A）在有丝分裂退出时主要有丝分裂激酶Cdk 1的靶点去磷酸化中起主要作用，但对其在有丝分裂进程中的调控机制知之甚少。在这里，我们表明，突变的催化或调节双胞胎/B55亚基的PP 2A作为增强子的gwl（Scant），获得功能等位基因的长城激酶基因，导致胚胎致死率在果蝇时，母体剂量的有丝分裂激酶波罗减少。我们还表明，杂合突变的内翻等位基因抑制杂合gwl（Scant），更多的胚胎存活。此外，杂合的PP 2A突变使强突变波罗（11）的杂合雌性部分不育，即使在没有gwl的情况下（Scant）。endos突变的杂合性抑制这种PP 2A/波罗（11）不育。endos的纯合突变或敲低导致提示维持有丝分裂状态的缺陷的表型。与gwl（Scant）显性突变体所显示的遗传相互作用雅阁，在培养细胞中敲低Endos的有丝分裂缺陷可以通过敲低PP 2A的催化亚基或Twins/B55调节亚基而被抑制，但不能通过果蝇PP 2A的其他三个调节B亚基。Greatwall在单个位点Ser 68磷酸化Endos，这是Endos功能所必需的。总之，这些相互作用表明，长城和Endos的行为，以促进失活的PP 2A-Twins/B55在果蝇。我们讨论了参与波罗激酶在这样一个调节回路。
Protein phosphatase 2A (PP2A) plays a major role in dephosphorylating the targets of the major mitotic kinase Cdk1 at mitotic exit, yet how it is regulated in mitotic progression is poorly understood. Here we show that mutations in either the catalytic or regulatory twins/B55 subunit of PP2A act as enhancers of gwl(Scant), a gain-of-function allele of the Greatwall kinase gene that leads to embryonic lethality in Drosophila when the maternal dosage of the mitotic kinase Polo is reduced. We also show that heterozygous mutant endos alleles suppress heterozygous gwl(Scant); many more embryos survive. Furthermore, heterozygous PP2A mutations make females heterozygous for the strong mutation polo(11) partially sterile, even in the absence of gwl(Scant). Heterozygosity for an endos mutation suppresses this PP2A/polo(11) sterility. Homozygous mutation or knockdown of endos leads to phenotypes suggestive of defects in maintaining the mitotic state. In accord with the genetic interactions shown by the gwl(Scant) dominant mutant, the mitotic defects of Endos knockdown in cultured cells can be suppressed by knockdown of either the catalytic or the Twins/B55 regulatory subunits of PP2A but not by the other three regulatory B subunits of Drosophila PP2A. Greatwall phosphorylates Endos at a single site, Ser68, and this is essential for Endos function. Together these interactions suggest that Greatwall and Endos act to promote the inactivation of PP2A-Twins/B55 in Drosophila. We discuss the involvement of Polo kinase in such a regulatory loop.