Phosphorylation of MyoGEF on Thr-574 by Plk1 promotes MyoGEF localization to the central spindle

J Biol Chem. 2008 Oct 17;283(42):28392-400. doi: 10.1074/jbc.M801801200. Epub 2008 Aug 11.


We reported previously that a guanine nucleotide exchange factor, MyoGEF, localizes to the central spindle, activates RhoA, and is required for cytokinesis. In this study, we have found that Plk1 (polo-like kinase 1) can phosphorylate MyoGEF, thereby recruiting MyoGEF to the central spindle as well as enhancing MyoGEF activity toward RhoA. The in vitro kinase assay shows that Plk1 can phosphorylate MyoGEF on threonine 574. Immunoprecipitation/immunoblot analysis demonstrates that mutation of threonine 574 to alanine dramatically decreases threonine phosphorylation of MyoGEF in transfected HeLa cells, suggesting that threonine 574 is phosphorylated in vivo. Consistent with these observations, immunofluorescence shows that Plk1 and MyoGEF colocalize at the spindle pole and central spindle during mitosis and cytokinesis. Importantly, RNA interference-mediated depletion of Plk1 interferes with the localization of MyoGEF at the spindle pole and central spindle. Moreover, mutation of threonine 574 to alanine in MyoGEF or depletion of Plk1 by RNA interference leads to a decrease in MyoGEF activity toward RhoA in HeLa cells. Therefore, our results suggest that Plk1 can regulate MyoGEF activity and localization, contributing to the regulation of cytokinesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / chemistry
  • Cell Cycle
  • Cell Cycle Proteins / chemistry
  • Cell Cycle Proteins / physiology*
  • Cytokinesis
  • Guanine Nucleotide Exchange Factors / chemistry*
  • HeLa Cells
  • Humans
  • Microscopy, Fluorescence / methods
  • Mitosis
  • Models, Biological
  • Phosphorylation
  • Plasmids / metabolism
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / physiology*
  • Proto-Oncogene Proteins / chemistry
  • Proto-Oncogene Proteins / physiology*
  • RNA / chemistry
  • Spindle Apparatus*
  • Threonine / chemistry*


  • Cell Cycle Proteins
  • Guanine Nucleotide Exchange Factors
  • PLEKHG6 protein, human
  • Proto-Oncogene Proteins
  • Threonine
  • RNA
  • Protein-Serine-Threonine Kinases
  • polo-like kinase 1
  • Alanine