Spc42p: a phosphorylated component of the S. cerevisiae spindle pole body (SPD) with an essential function during SPB duplication.
The 42-kD component of the S. cerevisiae spindle pole body (SPB) localizes to the electron-dense central plaque of the SPB. We have cloned the corresponding gene SPC42 (spindle pole component) and show that it is essential. Seven temperature-sensitive (ts) mutants in SPC42 were prepared by error-prone PCR. We found that a change to a proline residue in a potential coiled-coil region of Spc42p was responsible for the ts phenotype in at least three alleles, suggesting that formation of the coiled-coil is essential in normal function. The mutant cells showed a phenotype of predominantly single or bilobed SPBs often with an accumulation of unstructured electron-dense material associated with the bridge structure adjacent to the SPB. This phenotype suggests a defect in SPB duplication. This was confirmed by examining synchronized mutant cells that lose viability when SPB duplication is attempted. Spc42p is a phosphoprotein which shows some cell cycle-regulated phosphorylation. Overexpression of Spc42p causes the formation of a disc- or dome-shaped polymer composed of phosphorylated Spc42p, which is attached to the central plaque and associated with the outer nuclear membrane. Taken together, these data suggest that Spc42p forms a polymeric layer at the periphery of the SPB central plaque which has an essential function during SPB duplication and may facilitate attachment of the SPB to the nuclear membrane.
Donaldson
A D
AD
MRC Laboratory of Molecular Biology, Cambridge, England.
Kilmartin
J V
JV
D000908:Antibodies, Fungal; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D002453:Cell Cycle; D002458:Cell Fractionation; D018385:Centrosome / Q000502:physiology* / Q000648:ultrastructure; D003001:Cloning, Molecular; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000276:immunology / Q000502:physiology*; D005786:Gene Expression Regulation; D005800:Genes, Fungal; D008970:Molecular Weight; D016296:Mutagenesis; D010641:Phenotype; D010750:Phosphoproteins / Q000276:immunology / Q000502:physiology*; D010766:Phosphorylation; D011233:Precipitin Tests; D011994:Recombinant Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D017422:Sequence Analysis, DNA; D008941:Spindle Apparatus / Q000502:physiology* / Q000648:ultrastructure
D000908:Antibodies, Fungal; D000911:Antibodies, Monoclonal; D005656:Fungal Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins