Degradation of a cohesin subunit by the N-end rule pathway is essential for chromosome stability.
Cohesion between sister chromatids is established during DNA replication and depends on a protein complex called cohesin. At the metaphase-anaphase transition in the yeast Saccharomyces cerevisiae, the ESP1-encoded protease separin cleaves SCC1, a subunit of cohesin with a relative molecular mass of 63,000 (Mr 63K). The resulting 33K carboxy-terminal fragment of SCC1 bears an amino-terminal arginine-a destabilizing residue in the N-end rule. Here we show that the SCC1 fragment is short-lived (t1/2 approximately 2 min), being degraded by the ubiquitin/proteasome-dependent N-end rule pathway. Overexpression of a long-lived derivative of the SCC1 fragment is lethal. In ubr1Delta cells, which lack the N-end rule pathway, we found a highly increased frequency of chromosome loss. The bulk of increased chromosome loss in ubr1Delta cells is caused by metabolic stabilization of the ESP1-produced SCC1 fragment. This fragment is the first physiological substrate of the N-end rule pathway that is targeted through its N-terminal residue. A number of yeast proteins bear putative cleavage sites for the ESP1 separin, suggesting other physiological substrates and functions of the N-end rule pathway.
Rao
H
H
Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
Uhlmann
F
F
Nasmyth
K
K
Varshavsky
A
A
D000705:Anaphase; D001120:Arginine; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002455:Cell Division; D002842:Chromatids / Q000502:physiology; D002868:Chromosomal Proteins, Non-Histone; D020090:Chromosome Segregation; D015825:Chromosomes, Fungal / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism; D010450:Endopeptidases; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006207:Half-Life; D008025:Ligases; D009097:Multienzyme Complexes / Q000378:metabolism; D009687:Nuclear Proteins; D010446:Peptide Fragments / Q000378:metabolism; D010750:Phosphoproteins; D046988:Proteasome Endopeptidase Complex; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D064247:Separase; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism; D000098550:Structural Maintenance of Chromosome Protein 1
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004151:Dipeptides; D005656:Fungal Proteins; C490529:MCD1 protein, S cerevisiae; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; D000098550:Structural Maintenance of Chromosome Protein 1; D001120:Arginine; C066066:UBR1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; C577986:ESP1 protein, S cerevisiae; D064247:Separase; D046988:Proteasome Endopeptidase Complex; D008025:Ligases