Greatwall kinase participates in the Cdc2 autoregulatory loop in Xenopus egg extracts.
Mutations in the Drosophila gene encoding the serine-threonine protein kinase Greatwall have previously been shown to disrupt mitotic progression. To investigate Greatwall's mitotic function, we examined its behavior in Xenopus egg extracts. Greatwall is activated during mitosis by phosphorylation; in vitro evidence indicates that maturation promoting factor (MPF) is an upstream kinase. Conversely, depletion of Greatwall from mitotic extracts rapidly lowers MPF activity due to the accumulation of inhibitory phosphorylations on Cdc2 kinase. Greatwall depletion similarly prevents cycling extracts from entering M phase. The effects of Greatwall depletion can be rescued by the addition of either wild-type (wt) Greatwall or a noninhibitable form of Cdc2 kinase. These results demonstrate that Greatwall participates in an autoregulatory loop that generates and maintains sufficiently high MPF activity levels to support mitosis.
Yu
Jiangtao
J
Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.
Zhao
Yong
Y
Li
ZeXiao
Z
Galas
Simon
S
Goldberg
Michael L
ML
D000818:Animals; D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002455:Cell Division; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D016200:Maturation-Promoting Factor / Q000378:metabolism; D008938:Mitosis; D010063:Ovum / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D014982:Xenopus laevis
D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; C490167:Gwl protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor