title: Absence of reciprocal feedback between MPF and ERK2 MAP kinase in mitotic Xenopus laevis embryo cell-free extract.
abstract: MPF and MAP kinase ERK2 are two major M-phase kinases. They interact with each other in a complex way during meiotic maturation of Xenopus laevis oocytes. Here we study their interrelationship during first mitosis in X. laevis embryo cell-free extract perturbing the polyubiquitination pathway as a tool. Recombinant ubiquitin K48R (Ub-K48R) mutant protein arrests mitotic cyclin B degradation in the extract. This results in both increased accumulation of phosphorylated form of cyclin B2 and MPF activity as well as mitotic phosphorylation of its substrates. Ub-K48R also increased the mitotic phosphorylation of ERK2. Simultaneous addition of Ub-K48R and the proteasome inhibitor MG 132 strengthened and further prolonged MPF activity, MCM4 phosphorylation and accumulation of phosphorylated forms of cyclin B2. ERK2 phosphorylation levels increased and persisted longer than upon action of Ub-K48R alone. This shows a synergistic effect of inhibition of two different steps of ubiquitin-proteasome pathway on MPF activity and mitotic phosphorylation and ubiquitination of specific M-phase proteins. On the other hand, complete inhibition of ERK2 activation using U0126 had no effect either on MPF activity or on MCM4 phosphorylation either in control or in Ub-K48R-supplemented extracts. Experimental reduction of MPF activity by addition of recombinant p21(Cip) protein resulted in significant reduction of ERK2 phosphorylation. Thus, the reciprocal feedback observed between MPF and ERK2 in meiosis is not observed during mitotic M-phase in cell-free Xenopus embryo extracts. ERK2 phosphorylation is regulated by the levels of MPF activity, however no influence of ERK2 on MPF activity could be detected. These results show a fundamental difference in the relationship between the two major M-phase kinases in meiotic and mitotic cell cycle.
authors.affiliation: Biology and Genetics of Development, Mitosis and Meiosis Group, Institute of Genetics and Development of Rennes, University Rennes, Rennes Cedex, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Bazile
authors.forename: Aude
authors.initials: A
authors.lastname: Pascal
authors.forename: Anthi
authors.initials: A
authors.lastname: Karaiskou
authors.forename: Franck
authors.initials: F
authors.lastname: Chesnel
authors.forename: Jacek Z
authors.initials: JZ
authors.lastname: Kubiak
mesh_terms: D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002474:Cell-Free System; D004625:Embryo, Nonmammalian / Q000201:enzymology; D025461:Feedback, Physiological; D005260:Female; D007976:Leupeptins / Q000494:pharmacology; D016200:Maturation-Promoting Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008540:Meiosis / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology*; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D061988:Proteasome Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D029867:Xenopus Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D002070:Butadienes; D007976:Leupeptins; D009570:Nitriles; D061988:Proteasome Inhibitors; D047428:Protein Kinase Inhibitors; C113580:U 0126; D025801:Ubiquitin; D029867:Xenopus Proteins; D016200:Maturation-Promoting Factor; D019950:Mitogen-Activated Protein Kinase 1; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde