title: Oxidative stress responses involve oxidation of a conserved ubiquitin pathway enzyme.
abstract: Although it is vital that cells detect and respond to oxidative stress to allow adaptation and repair damage, the underlying sensing and signaling mechanisms that control these responses are unclear. Protein ubiquitinylation plays an important role in controlling many biological processes, including cell division. In Saccharomyces cerevisiae, ubiquitinylation involves a single E1 enzyme, Uba1, with multiple E2s and E3s providing substrate specificity. For instance, the conserved E2 Cdc34 ubiquitinylates many substrates, including the cyclin-dependent kinase inhibitor Sic1, targeting it for degradation to allow cell cycle progression. Here we reveal that, in contrast to other ubiquitin pathway E2 enzymes, Cdc34 is particularly sensitive to oxidative inactivation, through sequestration of the catalytic cysteine in a disulfide complex with Uba1, by levels of oxidant that do not reduce global ubiquitinylation of proteins. This Cdc34 oxidation is associated with (i) reduced levels of Cdc34-ubiquitin thioester forms, (ii) increased stability of at least one Cdc34 substrate, Sic1, and (iii) Sic1-dependent delay in cell cycle progression. Together, these data reveal that the differential sensitivity of a ubiquitin pathway E2 enzyme to oxidation is utilized as a stress-sensing mechanism to respond to oxidative stress.
authors.affiliation: Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, Tyne and Wear, United Kingdom.
authors.forename: Kathryn S
authors.initials: KS
authors.lastname: Doris
authors.forename: Ellen L
authors.initials: EL
authors.lastname: Rumsby
authors.forename: Brian A
authors.initials: BA
authors.lastname: Morgan
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D002453:Cell Cycle; D002455:Cell Division; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018384:Oxidative Stress; D017382:Reactive Oxygen Species; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D025801:Ubiquitin; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D017382:Reactive Oxygen Species; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D006861:Hydrogen Peroxide; C577449:CDC34 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044764:Ubiquitin-Activating Enzymes