Phosphorylation of Spc110p by Cdc28p-Clb5p kinase contributes to correct spindle morphogenesis in S. cerevisiae.
Spindle morphogenesis is regulated by cyclin-dependent kinases and monitored by checkpoint pathways to accurately coordinate chromosomal segregation with other events in the cell cycle. We have previously dissected the contribution of individual B-type cyclins to spindle morphogenesis in Saccharomyces cerevisiae. We showed that the S-phase cyclin Clb5p is required for coupling spindle assembly and orientation. Loss of Clb5p-dependent kinase abolishes intrinsic asymmetry between the spindle poles resulting in lethal translocation of the spindle into the bud with high penetrance in diploid cells. This phenotype was exploited in a screen for high dosage suppressors that yielded spc110(Delta)(13), encoding a truncation of the spindle pole body component Spc110p (the intranuclear receptor for the gamma-tubulin complex). We found that Clb5p-GFP was localised to the spindle poles and intranuclear microtubules and that Clb5p-dependent kinase promoted cell cycle dependent phosphorylation of Spc110p contributing to spindle integrity. Two cyclin-dependent kinase consensus sites were required for this phosphorylation and were critical for the activity of spc110(Delta)(13) as a suppressor. Together, our results point to the function of cyclin-dependent kinase phosphorylation of Spc110p and provide, in addition, support to a model for Clb5p control of spindle polarity at the level of astral microtubule organisation.
Huisman
Stephen M
SM
Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, UK.
Smeets
Monique F M A
MF
Segal
Marisa
M
D017489:CDC28 Protein Kinase, S cerevisiae / Q000235:genetics / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins / Q000378:metabolism*; D009024:Morphogenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000502:physiology*
D002148:Calmodulin-Binding Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; C073277:SPC110 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D017489:CDC28 Protein Kinase, S cerevisiae