Suppressors of the ndc10-2 mutation: a role for the ubiquitin system in Saccharomyces cerevisiae kinetochore function.
We have isolated a new conditional-lethal mutation, ndc10-2, in the NDC10/CBF2/CTF14 gene that encodes the 110-kD subunit of the Saccharomyces cerevisiae CBF3 kinetochore complex. At the restrictive temperature of 37 degrees, ndc10-2 cells are able to assemble anaphase spindles, but fail to segregate their DNA, consistent with a defect in kinetochore function. To identify other factors that play a role in kinetochore assembly or function, we isolated both dosage and second site suppressors of the ndc10-2 mutation. These screens identified UBC6 as a dosage suppressor, and mutations in UBC6 and UBC7 as second-site suppressors of ndc10-2 heat sensitivity. Both UBC6 and UBC7 encode ubiquitin-conjugating enzymes that function in ubiquitin-mediated protein degradation. Furthermore, overexpression of a mutant ubiquitin suppresses the ndc10-2 mutation. These results implicate the ubiquitin system in the regulation of ndc10-2 function and suggest a role for the ubiquitin system in kinetochore function.
Kopski
K M
KM
Section of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, New York 14853-2703, USA.
Huffaker
T C
TC
D064173:Anaphase-Promoting Complex-Cyclosome; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D018628:Gene Dosage; D005804:Genes, Lethal; D016153:Genes, Suppressor; D006358:Hot Temperature; D018386:Kinetochores / Q000502:physiology*; D008025:Ligases / Q000235:genetics; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*
C081071:CBF2 protein, S cerevisiae; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D008025:Ligases