Multiple roles for protein phosphatase 1 in regulating the Xenopus early embryonic cell cycle

D. H. Walker, A. A. DePaoli-Roach, J. L. Maller

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Abstract

Using cytostatic factor metaphase II-arrested extracts as a model system, we show that protein phosphatase 1 is regulated during early embryonic cell cycles in Xenopus. Phosphatase 1 activity peaks during interphase and decreases shortly before the onset of mitosis. A second peak of activity appears in mitosis at about the same time that cdc2 becomes active. If extracts are inhibited in S-phase with aphidicolin, then phosphatase 1 activity remains high. The activity of phosphatase 1 appears to determine the timing of exit from S-phase and entry into M-phase; inhibition of phosphatase 1 by the specific inhibitor, inhibitor 2 (Inh-2), causes premature entry into mitosis, whereas exogenously added phosphatase 1 lengthens the interphase period. Analysis of DNA synthesis in extracts treated with Inh-2, but lacking the A- and B-type cyclins, shows that phosphatase 1 is also required for the process of DNA replication. These data indicate that phosphatase 1 is a component of the signaling pathway that ensures that M-phase is not initiated until DNA synthesis is complete.

Original languageEnglish (US)
Pages (from-to)687-698
Number of pages12
JournalMolecular Biology of the Cell
Volume3
Issue number6
DOIs
StatePublished - Jan 1 1992

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ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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