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Letters to Nature
Nature 398, 246-251 (18 March 1999) | doi:10.1038/18457; Received 16 December 1998; Accepted 14 February 1999
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A new protease required for cell-cycle progression in yeast
Shyr-Jiann Li1 & Mark Hochstrasser1
- University of Chicago, Department of Biochemistry & Molecular Biology, 920 East 58th Street, Chicago, Illinois 60637, USA
Correspondence to: Mark Hochstrasser1 Correspondence and requests for materials should be addressed to M.H. (e-mail: Email: hoc1@midway.uchicago.edu).
Abstract
In eukaryotes, protein function can be modulated by ligation to ubiquitin or to ubiquitin-like proteins (Ubl proteins)1, 2, 3. The vertebrate Ubl protein SUMO-1 is only 18% identical to ubiquitin but is 48% identical to the yeast protein Smt3. Both SUMO-1 and Smt3 are ligated to cellular proteins, and protein conjugation to SUMO-1/Smt3 is involved in many physiological processes3, 4, 5, 6, 7, 8, 9, 10. It remained unknown, however, whether deconjugation of SUMO-1/Smt3 from proteins is also essential. Here we describe a yeast Ubl-specific protease, Ulp1, which cleaves proteins from Smt3 and SUMO-1 but not from ubiquitin. Ulp1 is unrelated to any known deubiquitinating enzyme but shows distant similarity to certain viral proteases, indicating the existence of a widely conserved protease fold. Proteins related to Ulp1 are present in many organisms, including several human pathogens. The pattern of Smt3-coupled proteins in yeast changes markedly throughout the cell cycle, and specific conjugates accumulate in ulp1 mutants. Ulp1 has several functions, including an essential role in the G2/M phase of the cell cycle.
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