Sgt1p and Skp1p modulate the assembly and turnover of CBF3 complexes required for proper kinetochore function.
Kinetochores are composed of a large number of protein complexes that must be properly assembled on DNA to attach chromosomes to the mitotic spindle and to coordinate their segregation with the advance of the cell cycle. CBF3 is an inner kinetochore complex in the budding yeast Saccharomyces cerevisiae that nucleates the recruitment of all other kinetochore proteins to centromeric DNA. Skp1p and Sgt1p act through the core CBF3 subunit, Ctf13p, and are required for CBF3 to associate with centromeric DNA. To investigate the contribution of Skp1p and Sgt1p to CBF3 function, we have used a combination of in vitro binding assays and a unique protocol for synchronizing the assembly of kinetochores in cells. We have found that the interaction between Skp1p and Sgt1p is critical for the assembly of CBF3 complexes. CBF3 assembly is not restricted during the cell cycle and occurs in discrete steps; Skp1p and Sgt1p contribute to a final, rate-limiting step in assembly, the binding of the core CBF3 subunit Ctf13p to Ndc10p. The assembly of CBF3 is opposed by its turnover and disruption of this balance compromises kinetochore function without affecting kinetochore formation on centromeric DNA.
Rodrigo-Brenni
Monica C
MC
Section of Molecular and Cellular Biology, University of California, Davis, Davis, California 95616, USA.
Thomas
Scott
S
Bouck
David C
DC
Kaplan
Kenneth B
KB
D048868:Adaptor Proteins, Signal Transducing; D020090:Chromosome Segregation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D018386:Kinetochores / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C081071:CBF2 protein, S cerevisiae; C081354:CTF13 protein, S cerevisiae; D004268:DNA-Binding Proteins; D044783:F-Box Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; C470726:SGT1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D044843:SKP Cullin F-Box Protein Ligases; C120507:SKP1 protein, S cerevisiae; D005947:Glucose