title: Polo boxes form a single functional domain that mediates interactions with multiple proteins in fission yeast polo kinase.
abstract: Polo kinases play multiple roles in cell cycle regulation in eukaryotic cells. In addition to the kinase domain, conservation at the primary sequence level is also found in the non-catalytic region mainly in three blocks, namely the polo boxes. Although several studies have implicated the polo boxes in protein localisation, no systematic study to elucidate the roles of individual polo boxes has been carried out. Here we show, by using fission yeast, that the polo boxes form a single functional unit that is essential for both cellular function and cell-cycle-regulated localisation to the spindle pole bodies. Various polo box mutations abolish the mitotic arrest seen upon overexpression of plo1 but do not prevent the untimely septation seen under these conditions, showing that the functions of Plo1 may be separated. Plo1 interacts with multiple proteins including cell cycle regulators in a polo-box-dependent manner. Isolation of mutants that differentially disrupt these interactions revealed a role for the polo boxes in mediating protein-protein interactions.
authors.affiliation: The Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, The University of Edinburgh, Edinburgh EH9 3JR, UK.
authors.forename: Nicola
authors.initials: N
authors.lastname: Reynolds
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohkura
mesh_terms: D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins; D018816:Genes, cdc / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D012568:Schizosaccharomyces / Q000201:enzymology*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D008941:Spindle Apparatus / Q000201:enzymology* / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D029702:Schizosaccharomyces pombe Proteins; D017346:Protein Serine-Threonine Kinases