Dual Function of the Germinal Centre Kinase Don3 During Mitosis and Cytokinesis in Ustilago Maydis

Mol Microbiol. 2006 Nov;62(3):655-66. doi: 10.1111/j.1365-2958.2006.05405.x. Epub 2006 Sep 25.


Septum formation is a crucial step of cytokinesis in fungi. In the basidiomycete Ustilago maydis, the germinal centre kinase Don3 triggers initiation of a secondary septum necessary for cell separation after cytokinesis. Here we show that oligomerization of Don3 via a putative coiled-coil domain is critical for secondary septum formation. Within the Don3 sequence we detected a characteristic C-terminal sequence motif (T-motif), which determines the subcellular localization of Don3 but is not required for regulation of cell separation. This motif defines a novel family of fungal protein kinases including Sid1p, an essential component of the septation initiation network (SIN) in Schizosaccharomyces pombe. Using the yeast two-hybrid system we isolated the Don3-interacting protein Dip1, which is similar to S. pombe Cdc14p, another member of the SIN. Remarkably, deletion of dip1 did not interfere with cytokinesis in U. maydis, but both dip1 and don3 mutants were affected in nuclear envelope breakdown (NEBD) during mitosis. This phenotype has already been described for mutants, which lack the small GTPase Ras3, the U. maydis homologue of the SIN component Spg1p. We propose that the Don3 kinase exerts a dual function in the regulation of cell separation and NEBD.

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Cycle Proteins / metabolism
  • Cytokinesis*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • GTP Phosphohydrolases / genetics
  • GTP Phosphohydrolases / metabolism
  • Germinal Center Kinases
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Mitosis*
  • Molecular Sequence Data
  • Mutation
  • Nuclear Envelope / genetics
  • Nuclear Envelope / metabolism
  • Protein Kinases / metabolism
  • Protein Structure, Tertiary
  • Protein Tyrosine Phosphatases / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Two-Hybrid System Techniques
  • Ustilago / cytology
  • Ustilago / enzymology*
  • Ustilago / genetics
  • ras Proteins / genetics
  • ras Proteins / metabolism


  • CDC14 protein, S cerevisiae
  • Carrier Proteins
  • Cell Cycle Proteins
  • Fungal Proteins
  • Germinal Center Kinases
  • Intracellular Signaling Peptides and Proteins
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins
  • Protein Kinases
  • Sid1 kinase
  • Protein-Serine-Threonine Kinases
  • Protein Tyrosine Phosphatases
  • GTP Phosphohydrolases
  • Spg1 protein, S pombe
  • ras Proteins