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Proper timing of cytokinesis is regulated by Schizosaccharomyces pombe Etd1

¹ Department of Molecular Genetics and Microbiology and ² Program in Cell Dynamics, University of Massachusetts Medical School, Worcester, MA 01655

Correspondence to Dannel McCollum: dannel.mccollum{at}umassmed.edu

Cytokinesis must be initiated only after chromosomes have been segregated in anaphase and must be terminated once cleavage is completed. We show that the fission yeast protein Etd1 plays a central role in both of these processes. Etd1 activates the guanosine triphosphatase (GTPase) Spg1 to trigger signaling through the septum initiation network (SIN) pathway and onset of cytokinesis. Spg1 is activated in late anaphase when spindle elongation brings spindle pole body (SPB)–localized Spg1 into proximity with its activator Etd1 at cell tips, ensuring that cytokinesis is only initiated when the spindle is fully elongated. Spg1 is active at just one of the two SPBs during cytokinesis. When the actomyosin ring finishes constriction, the SIN triggers disappearance of Etd1 from the half of the cell with active Spg1, which then triggers Spg1 inactivation. Asymmetric activation of Spg1 is crucial for timely inactivation of the SIN. Together, these results suggest a mechanism whereby cell asymmetry is used to monitor cytoplasmic partitioning to turn off cytokinesis signaling.

Abbreviations used in this paper: APC, anaphase-promoting complex; CHD, Cdc25 homology domain; CW, calcofluor white; DIC, differential interference contrast; EMM, Edinburgh minimal medium; GAP, GTPase-activating protein; GEF, guanine nucleotide exchange factor; MBC, methyl-2-benzimidazole-carbamate; MBP, maltose-binding protein; MEN, mitotic exit network; SIN, septum initiation network; SPB, spindle pole body; YE, yeast extract.

© 2009 García-Cortés and McCollum
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