The protein kinase kin1, the fission yeast orthologue of mammalian MARK/PAR-1, localises to new cell ends after mitosis and is important for bipolar growth.
The kin1 protein kinase of the fission yeast Schizosaccharomyces pombe is a member of the PAR-1/MARK (partitioning-defective 1/microtubule-associated protein/microtubule affinity-regulating kinase) family important in eukaryotic cell polarity and cytoskeletal dynamics. We show here that kin1 plays a role in establishing the characteristic rod-shaped morphology of fission yeast. Cells in which kin1 was deleted are viable but are impaired in growth, and are rounded at one end or both ends. They are monopolar because after mitosis they fail to activate bipolar growth, and are delayed in cytokinesis, resulting in a high proportion of septated cells often with multiple septa. This phenotype can be partially rescued by heterologous expression of human MARKs, which restore bipolar growth in most cells, but do not correct the delay in cytokinesis. Using chromosomal epitope tagging, we show that kin1p localises to the cell ends, except during mitosis when it disappears from cell ends. After mitosis, kin1p first reappears at the new cell end. Overexpression of kin1 results in a loss of polarity, with partially or fully rounded cells. From these results we suggest that kin1 is required to direct the growth machinery to the cell ends.
Drewes
Gerard
G
Cell Cycle Laboratory, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. gerard.drewes@cellzome.com
Nurse
Paul
P
D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000502:physiology*; D002455:Cell Division; D016764:Cell Polarity; D048429:Cell Size; D005656:Fungal Proteins / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008938:Mitosis; D010750:Phosphoproteins / Q000378:metabolism* / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D021381:Protein Transport; D051381:Rats; D012568:Schizosaccharomyces / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins; D019076:Transgenes
D029742:Caenorhabditis elegans Proteins; D005656:Fungal Proteins; D010750:Phosphoproteins; D029702:Schizosaccharomyces pombe Proteins; C105547:MARK1 protein, human; C105549:MARK2 protein, rat; C111833:MARK3 protein, human; C484552:Mark1 protein, rat; D017346:Protein Serine-Threonine Kinases; C087571:kin1 protein, S pombe