A chaperone-assisted degradation pathway targets kinetochore proteins to ensure genome stability.
Cells are regularly exposed to stress conditions that may lead to protein misfolding. To cope with this challenge, molecular chaperones selectively target structurally perturbed proteins for degradation via the ubiquitin-proteasome pathway. In mammals the co-chaperone BAG-1 plays an important role in this system. BAG-1 has two orthologues, Bag101 and Bag102, in the fission yeast Schizosaccharomyces pombe. We show that both Bag101 and Bag102 interact with 26S proteasomes and Hsp70. By epistasis mapping we identify a mutant in the conserved kinetochore component Spc7 (Spc105/Blinkin) as a target for a quality control system that also involves, Hsp70, Bag102, the 26S proteasome, Ubc4 and the ubiquitin-ligases Ubr11 and San1. Accordingly, chromosome missegregation of spc7 mutant strains is alleviated by mutation of components in this pathway. In addition, we isolated a dominant negative version of the deubiquitylating enzyme, Ubp3, as a suppressor of the spc7-23 phenotype, suggesting that the proteasome-associated Ubp3 is required for this degradation system. Finally, our data suggest that the identified pathway is also involved in quality control of other kinetochore components and therefore likely to be a common degradation mechanism to ensure nuclear protein homeostasis and genome integrity.
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Franziska
F
Kriegenburg
Lehrstuhl für Funktionelle Genomforschung der Mikroorganismen, Heinrich-Heine Universität, Düsseldorf, Germany.
Visnja
V
Jakopec
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Esben G
EG
Poulsen
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Sofie Vincents
SV
Nielsen
Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America.
Assen
A
Roguev
Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America.
Nevan
N
Krogan
MRC Human Genetics Unit, Western General Hospital, Edinburgh, Scotland, United Kingdom.
Colin
C
Gordon
Lehrstuhl für Funktionelle Genomforschung der Mikroorganismen, Heinrich-Heine Universität, Düsseldorf, Germany.
Ursula
U
Fleig
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Rasmus
R
Hartmann-Petersen
D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D042822:Genomic Instability; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018386:Kinetochores; D018832:Molecular Chaperones / Q000235:genetics* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000235:genetics; D059748:Proteolysis; D012568:Schizosaccharomyces; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000235:genetics
C091732:BCL2-associated athanogene 1 protein; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; D025801:Ubiquitin; C558901:San1 protein, S pombe; D044767:Ubiquitin-Protein Ligases; C582094:Ubr11 protein, S pombe; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease