The human homologue of the yeast polyubiquitination factor Ufd2p is cleaved by caspase 6 and granzyme B during apoptosis.
In the present study, we demonstrate that a human homologue of Ufd2p (a yeast protein that catalyses the formation of long polyubiquitin chains, and is implicated in responses to environmental stress), UFD2 (ubiquitin fusion degradation protein-2), is cleaved during apoptosis induced by multiple stimuli, including UVB irradiation, Fas ligation, staurosporine treatment and cytotoxic lymphocyte granule-induced death. Caspase 6 and granzyme B efficiently cleave UFD2 [k(cat)/K(m)=(4-5) x 10(4) M(-1) x s(-1)] at Asp(123), whereas caspases 3 and 7 cleave UFD2 approx. 10-fold less efficiently immediately upstream at Asp(109). Thus UFD2 is added to the growing list of proteins with closely spaced caspase and granzyme B cleavage sites, suggesting the presence of a previously unrecognized, conserved motif. Both cleavage sites are contained and conserved within a novel 300-amino-acid N-terminal domain present in apparent UFD2 orthologues in mice and zebrafish, but absent in all UFD2 family members in lower eukaryotes. Full-length recombinant UFD2 exhibited ubiquitin-protein ligase ('E3')-like ubiquitination activity in vitro, but this activity was abolished in recombinant UFD2 truncated at the granzyme B/caspase 6 cleavage site. Cleavage of UFD2 by caspases or granzyme B within this putative regulatory N-terminal domain might have important functional consequences within the apoptotic cascade.
Pubmed ID: 11802788 RIS Download
Amino Acid Motifs | Amino Acid Sequence | Apoptosis | Baculoviridae | Binding Sites | Blotting, Northern | Caspase 6 | Caspases | Cloning, Molecular | Enzyme Inhibitors | Fungal Proteins | Granzymes | HeLa Cells | Humans | Kinetics | Molecular Sequence Data | Mutagenesis, Site-Directed | Precipitin Tests | Protein Binding | Protein Structure, Tertiary | Recombinant Proteins | Saccharomyces cerevisiae Proteins | Sequence Homology, Amino Acid | Serine Endopeptidases | Staurosporine | Tissue Distribution | Ubiquitin | Ubiquitin-Conjugating Enzymes | Ultraviolet Rays