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Mol Biol Cell 2008 Apr 01;194:1317-27. doi: 10.1091/mbc.e07-11-1099.
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Roles of Greatwall kinase in the regulation of cdc25 phosphatase.

Zhao Y , Haccard O , Wang R , Yu J , Kuang J , Jessus C , Goldberg ML .

We previously reported that immunodepletion of Greatwall kinase prevents Xenopus egg extracts from entering or maintaining M phase due to the accumulation of inhibitory phosphorylations on Thr14 and Tyr15 of Cdc2. M phase-promoting factor (MPF) in turn activates Greatwall, implying that Greatwall participates in an MPF autoregulatory loop. We show here that activated Greatwall both accelerates the mitotic G2/M transition in cycling egg extracts and induces meiotic maturation in G2-arrested Xenopus oocytes in the absence of progesterone. Activated Greatwall can induce phosphorylations of Cdc25 in the absence of the activity of Cdc2, Plx1 (Xenopus Polo-like kinase) or mitogen-activated protein kinase, or in the presence of an activator of protein kinase A that normally blocks mitotic entry. The effects of active Greatwall mimic in many respects those associated with addition of the phosphatase inhibitor okadaic acid (OA); moreover, OA allows cycling extracts to enter M phase in the absence of Greatwall. Taken together, these findings support a model in which Greatwall negatively regulates a crucial phosphatase that inhibits Cdc25 activation and M phase induction.

PubMed ID: 18199678
PMC ID: PMC2291418
Article link: Mol Biol Cell
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: alb camk2a camk2g camp ccnb1 ccnb2 cdc25c cdk1 mapk1 mastl mos myt1 plk1 rasgrf1 rps6ka1 uqcc6 wee1
Antibodies: Cdc2 Ab2 Cdk1 Ab2 Mapk1 Ab14 Mastl Ab1 Plk1 Ab1
Morpholinos: mos MO1

Article Images: [+] show captions
References [+] :
Abrieu, The Polo-like kinase Plx1 is a component of the MPF amplification loop at the G2/M-phase transition of the cell cycle in Xenopus eggs. 1998, Pubmed, Xenbase