Control of cytokinesis by the mitotic cyclin dependent kinase M-Cdk1 /

Resumen

Cytokinesis is the final regulated process in the eukaryotic mitotic cell division cycle. Cells enter cytokinesis once after chromosome segregation is satisfactorily completed. During cytokinesis cells physically separate, giving place to two daughter cells. Defects in the control of cytokinesis result in aneuploidies and genomic instability. A key controller of cytokinesis is the mitotic Cdk1 (M-Cdk1) activity. Our project derives from the observed correlation between the onset of cytokinesis and the termination of M-Cdk1 activity(Wäsch & Cross 2002)(Wäsch & Cross 2002)(Wäsch & Cross 2002). Complementary to such observation, expression of a hyperstable allele of the mitotic cyclin Clb2, blocks cytokinesis. Thus, the very same activity that pushes cells into mitosis and promotes mitotic entry and anaphase, blocks the occurrence of premature cytokinesis. These observations suggest that one or more proteins, essential to trigger cytokinesis, are inhibited by M-Cdk1 phosphorylation. The identity of such critical M-Cdk1 substrate/s is unknown. Therefore, the goal of this thesis is to gain insight on how M-Cdk1 prevents premature cytokinesis during anaphase in the model eukaryotic organism Saccharomyces cerevisiae. The thesis work reveals that the Mitotic Exit Network is unexpectedly partially activated in the presence of prevailing high M-Cdk1 activity, and drives the release of the Cdc14 phosphatase to the cytoplasm under such conditions.