Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Anaphase
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Arginine
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Cell Cycle Proteins / chemistry
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Cell Cycle Proteins / metabolism*
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Cell Division
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Chromatids / physiology
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Chromosomal Proteins, Non-Histone*
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Chromosome Segregation*
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Chromosomes, Fungal / physiology*
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Cysteine Endopeptidases / metabolism
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Dipeptides / metabolism
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Endopeptidases*
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Fungal Proteins / genetics
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Fungal Proteins / metabolism
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Half-Life
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Ligases*
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Multienzyme Complexes / metabolism
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Nuclear Proteins
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Peptide Fragments / metabolism
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Phosphoproteins
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Proteasome Endopeptidase Complex
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins*
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Separase
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Ubiquitin-Protein Ligases*
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Ubiquitins / metabolism
Substances
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Cell Cycle Proteins
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Chromosomal Proteins, Non-Histone
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Dipeptides
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Fungal Proteins
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MCD1 protein, S cerevisiae
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Multienzyme Complexes
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Nuclear Proteins
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Peptide Fragments
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Phosphoproteins
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Ubiquitins
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structural maintenance of chromosome protein 1
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Arginine
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UBR1 protein, S cerevisiae
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Ubiquitin-Protein Ligases
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Endopeptidases
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Cysteine Endopeptidases
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ESP1 protein, S cerevisiae
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Separase
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Proteasome Endopeptidase Complex
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Ligases