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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.

Original publication

DOI

10.1038/35073627

Type

Journal article

Journal

Nature

Publication Date

19/04/2001

Volume

410

Pages

955 - 959

Keywords

Anaphase, Arginine, Cell Cycle Proteins, Cell Division, Chromatids, Chromosomal Proteins, Non-Histone, Chromosome Segregation, Chromosomes, Fungal, Cysteine Endopeptidases, Dipeptides, Endopeptidases, Fungal Proteins, Half-Life, Ligases, Multienzyme Complexes, Nuclear Proteins, Peptide Fragments, Phosphoproteins, Proteasome Endopeptidase Complex, Recombinant Fusion Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Separase, Ubiquitin-Protein Ligases, Ubiquitins