Study of cyclin proteolysis in anaphase-promoting complex (APC) mutant cells reveals the requirement for APC function in the final steps of the fission yeast septation initiation network.

Chang L, Morrell JL, Feoktistova A, Gould KL
Mol Cell Biol. 2001 21 (19): 6681-94

PMID: 11533255 · PMCID: PMC99813 · DOI:10.1128/mcb.21.19.6681-6694.2001

Cytokinesis in eukaryotic cells requires the inactivation of mitotic cyclin-dependent kinase complexes. An apparent exception to this relationship is found in Schizosaccharomyces pombe mutants with mutations of the anaphase-promoting complex (APC). These conditional lethal mutants arrest with unsegregated chromosomes because they cannot degrade the securin, Cut2p. Although failing at nuclear division, these mutants septate and divide. Since septation requires Cdc2p inactivation in wild-type S. pombe, it has been suggested that Cdc2p inactivation occurs in these mutants by a mechanism independent of cyclin degradation. In contrast to this prediction, we show that Cdc2p kinase activity fluctuates in APC cut mutants due to Cdc13/cyclin B destruction. In APC-null mutants, however, septation and cutting do not occur and Cdc13p is stable. We conclude that APC cut mutants are hypomorphic with respect to Cdc13p degradation. Indeed, overproduction of nondestructible Cdc13p prevents septation in APC cut mutants and the normal reorganization of septation initiation network components during anaphase.

MeSH Terms (12)

Anaphase Anaphase-Promoting Complex-Cyclosome CDC2 Protein Kinase Cell Division Cyclin B Ligases Microscopy, Fluorescence Models, Biological Mutation Schizosaccharomyces Ubiquitin-Protein Ligase Complexes Ubiquitin-Protein Ligases

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