Dependence of Chs2 ER export on dephosphorylation by cytoplasmic Cdc14 ensures that septum formation follows mitosis

Mol Biol Cell. 2012 Jan;23(1):45-58. doi: 10.1091/mbc.E11-05-0434. Epub 2011 Nov 9.

Abstract

Cytokinesis, which leads to the physical separation of two dividing cells, is normally restrained until after nuclear division. In Saccharomyces cerevisiae, chitin synthase 2 (Chs2), which lays down the primary septum at the mother-daughter neck, also ensures proper actomyosin ring constriction during cytokinesis. During the metaphase-to-anaphase transition, phosphorylation of Chs2 by the mitotic cyclin-dependent kinase (Cdk1) retains Chs2 at the endoplasmic reticulum (ER), thereby preventing its translocation to the neck. Upon Cdk1 inactivation at the end of mitosis, Chs2 is exported from the ER and targeted to the neck. The mechanism for triggering Chs2 ER export thus far is unknown. We show here that Chs2 ER export requires the direct reversal of the inhibitory Cdk1 phosphorylation sites by Cdc14 phosphatase, the ultimate effector of the mitotic exit network (MEN). We further show that only Cdc14 liberated by the MEN after completion of chromosome segregation, and not Cdc14 released in early anaphase by the Cdc fourteen early anaphase release pathway, triggers Chs2 ER exit. Presumably, the reduced Cdk1 activity in late mitosis further favors dephosphorylation of Chs2 by Cdc14. Thus, by requiring declining Cdk1 activity and Cdc14 nuclear release for Chs2 ER export, cells ensure that septum formation is contingent upon chromosome separation and exit from mitosis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Actomyosin / metabolism
  • Amino Acid Substitution
  • CDC2 Protein Kinase / metabolism
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Nucleolus / metabolism
  • Chitin Synthase / genetics
  • Chitin Synthase / metabolism*
  • Cyclin-Dependent Kinase Inhibitor Proteins / metabolism
  • Cytokinesis
  • Endoplasmic Reticulum / enzymology*
  • Endoplasmic Reticulum / metabolism
  • Gene Knockout Techniques
  • Green Fluorescent Proteins / metabolism
  • Microscopy, Fluorescence
  • Mitosis*
  • Mutagenesis, Site-Directed
  • Phosphorylation
  • Protein Transport*
  • Protein Tyrosine Phosphatases / genetics
  • Protein Tyrosine Phosphatases / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Time-Lapse Imaging

Substances

  • CDC14 protein, S cerevisiae
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor Proteins
  • Recombinant Fusion Proteins
  • SIC1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Green Fluorescent Proteins
  • Actomyosin
  • Chitin Synthase
  • chitin synthase 2
  • CDC2 Protein Kinase
  • Protein Tyrosine Phosphatases