A MAP kinase-dependent spindle assembly checkpoint in Xenopus egg extracts.
Like early Xenopus embryos, extracts made from Xenopus eggs lack the cell cycle checkpoint that keeps anaphase from occurring before spindle assembly is complete. At very high densities of sperm nuclei, however, microtubule depolymerization arrests the extracts in mitosis. The arrested extracts have high levels of maturation-promoting factor activity, fail to degrade cyclin B, and contain activated ERK2/mitogen-activated protein (MAP) kinase. The addition of the purified MAP kinase-specific phosphatase MKP-1 demonstrates that MAP kinase activity is required for both the establishment and maintenance of the mitotic arrest induced by spindle depolymerization. Increased calcium concentrations, which release unfertilized frog eggs from their natural arrest in metaphase of meiosis II, have no effect on the mitotic arrest.
Department of Physiology, University of California, San Francisco 94143-0444.
J
J
Minshull
H
H
Sun
N K
NK
Tonks
A W
AW
Murray
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000502:physiology / Q000648:ultrastructure; D002474:Cell-Free System; D016213:Cyclins / Q000378:metabolism; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation; D038362:Glycogen Synthase Kinase 3; D006657:Histones / Q000378:metabolism; D017874:Immediate-Early Proteins / Q000378:metabolism; D008297:Male; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis / Q000502:physiology; D008954:Models, Biological; D015739:Nocodazole / Q000494:pharmacology; D010063:Ovum / Q000502:physiology; D017239:Paclitaxel / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D017231:Proto-Oncogene Proteins c-mos / Q000378:metabolism; D013094:Spermatozoa / Q000502:physiology; D008941:Spindle Apparatus / Q000187:drug effects / Q000502:physiology*; D014981:Xenopus
D018797:Cell Cycle Proteins; D016213:Cyclins; D006657:Histones; D017874:Immediate-Early Proteins; D017231:Proto-Oncogene Proteins c-mos; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases; D017239:Paclitaxel; D015739:Nocodazole; D002118:Calcium