Budding Yeast Swe1 is Involved in the Control of Mitotic Spindle Elongation and is Regulated by Cdc14 Phosphatase during Mitosis [Microbiology]

November 18th, 2014 by Raspelli, E., Cassani, C., Chiroli, E., Fraschini, R.

Cyclin-dependent kinase (Cdk1) activity is required for mitotic entry and this event is restrained by an inhibitory phosphorylation of the catalitic subunit Cdc28 on a conserved tyrosine (Y19). This modification is brought about by the protein kinase Swe1 that inhibits Cdk1 activation thus blocking mitotic entry. Swe1 levels are regulated during the cell cycle and decrease in G2/M concomitantly to Cdk1 activation that drives entry into mitosis. However, after mitotic entry, a pool of Swe1 persists and we collected evidences that it is involved in controlling mitotic spindle elongation. We also describe that the protein phosphatase Cdc14 is implicated in Swe1 regulation; in fact, we observed that Swe1 dephosphorylation in vivo depends on Cdc14 that, in turn, is able to control its subcellular localization. In addition we show that the lack of Swe1 causes premature mitotic spindle elongation and that, consistently, high levels of Swe1 block mitotic spindle elongation indicating that Swe1 inhibits this process. Importantly these effects are not dependent upon Swe1 role on Cdk1 inhibition. These data fit into a model in which Cdc14 binds and inhibits Swe1 in order to allow timely mitotic spindle elongation.
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