title: A novel mechanism for SUMO system control: regulated Ulp1 nucleolar sequestration.
abstract: The small ubiquitin-related modifiers (SUMOs) are evolutionarily conserved polypeptides that are covalently conjugated to protein targets to modulate their subcellular localization, half-life, or activity. Steady-state SUMO conjugation levels increase in response to many different types of environmental stresses, but how the SUMO system is regulated in response to these insults is not well understood. Here, we characterize a novel mode of SUMO system control: in response to elevated alcohol levels, the Saccharomyces cerevisiae SUMO protease Ulp1 is disengaged from its usual location at the nuclear pore complex (NPC) and sequestered in the nucleolus. We further show that the Ulp1 region previously demonstrated to interact with the karyopherins Kap95 and Kap60 (amino acids 150 to 340) is necessary and sufficient for nucleolar targeting and that enforced sequestration of Ulp1 in the nucleolus significantly increases steady-state SUMO conjugate levels, even in the absence of alcohol. We have thus characterized a novel mechanism of SUMO system control in which the balance between SUMO-conjugating and -deconjugating activities at the NPC is altered in response to stress via relocalization of a SUMO-deconjugating enzyme.
authors.affiliation: Ontario Cancer Institute, University of Toronto, MaRS TMDT 9-805, 101 College Street, Toronto, Ontario M5G 1L7, Canada.
authors.forename: Yaroslav
authors.initials: Y
authors.lastname: Sydorskyy
authors.forename: Tharan
authors.initials: T
authors.lastname: Srikumar
authors.forename: Stanley M
authors.initials: SM
authors.lastname: Jeram
authors.forename: Sarah
authors.initials: S
authors.lastname: Wheaton
authors.forename: Franco J
authors.initials: FJ
authors.lastname: Vizeacoumar
authors.forename: Taras
authors.initials: T
authors.lastname: Makhnevych
authors.forename: Yolanda T
authors.initials: YT
authors.lastname: Chong
authors.forename: Anne-Claude
authors.initials: AC
authors.lastname: Gingras
authors.forename: Brian
authors.initials: B
authors.lastname: Raught
mesh_terms: D000438:Alcohols / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism
chemical_list: D000438:Alcohols; D028884:Karyopherins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D028961:beta Karyopherins; D003546:Cysteine Endopeptidases; C118083:Ulp1 protease