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#mitotic CDKs

2 public questions tagged with this topic.

Cell Cycle Regulation

Which phosphatase deactivates mitotic CDKs to promote exit from mitosis?

Lowering mitotic kinase activity requires collaboration between ubiquitin mediated cyclin destruction and phosphatase mediated substrate dephosphorylation. APC/C-Cdc20 degrades cyclin B reducing CDK1 catalytic availability, but hundreds of phosphorylated residues remain. Phosphatases execute erasure. In yeast, Cdc14 is dominant enzyme preferentially dephosphorylating proline-directed CDK sites, including Cdh1 to activate APC/C-Cdh1 for further cyclin clearance, Swi5 for Sic1 transcription and structural cytokinesis proteins. In metazoa, PP2A-B55 family is major mitotic exit phosphatase regulat

Ref: Wurzenberger & Gerlich, Mitotic Phosphatases PP2A and Cdc14 in Exit, J Cell Biol 2011; NCBI Bookshelf, Regulation of Mitotic Exit.

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Cell Cycle Regulation

How do mitotic CDKs promote nuclear envelope breakdown?

Interphase nucleus bounded by double membrane supported by lamina composed of type V intermediate filaments lamin A/C, B1, B2 forming meshwork under inner nuclear membrane and linking to chromatin via emerin, LAP2 beta and LBR. Breakdown necessary for spindle access in metazoa relies on mitotic CDK1-Cyclin B catalyzed phosphorylation. CDK1 phosphorylates lamins at conserved sites flanking central alpha-helical rod: Ser22 and Ser392 on Lamin A/C cause electrostatic repulsion and disassembly of head-to-tail polymers into soluble dimers and tetramers. Concurrently CDK1 and Plk1 phosphorylate nucl

Ref: Guttinger et al., Mechanisms of Nuclear Envelope Breakdown and Reformation, Nat Rev Mol Cell Biol 2009; Alberts, Chapter 17.

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