title: New insight into the role of the Cdc34 ubiquitin-conjugating enzyme in cell cycle regulation via Ace2 and Sic1.
abstract: The Cdc34 ubiquitin-conjugating enzyme plays a central role in progression of the cell cycle. Through analysis of the phenotype of a mutant missing a highly conserved sequence motif within the catalytic domain of Cdc34, we discovered previously unrecognized levels of regulation of the Ace2 transcription factor and the cyclin-dependent protein kinase inhibitor Sic1. In cells carrying the Cdc34(tm) mutation, which alters the conserved sequence, the cyclin-dependent protein kinase inhibitor Sic1, an SCF(Cdc4) substrate, has a shorter half-life, while the cyclin Cln1, an SCF(Grr1) substrate, has a longer half-life than in wild-type cells. Expression of the SIC1 gene cluster, which is regulated by Swi5 and Ace2 transcription factors, is induced in CDC34(tm) cells. Levels of Swi5, Ace2, and the SCF(Grr1) targets Cln1 and Cln2 are elevated in Cdc34(tm) cells, and loss of Grr1 causes an increase in Ace2 levels. Sic1 levels are similar in CDC34(tm) ace2Δ and wild-type cells, explaining a paradoxical increase in the steady-state level of Sic1 protein despite its reduced half-life. A screen for mutations that interact with CDC34(tm) uncovered novel regulators of Sic1, including genes encoding the polyubiquitin chain receptors Rad23 and Rpn10.
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-2111, USA.
authors.forename: Ross
authors.initials: R
authors.lastname: Cocklin
authors.forename: Joshua
authors.initials: J
authors.lastname: Heyen
authors.forename: Tolonda
authors.initials: T
authors.lastname: Larry
authors.forename: Mike
authors.initials: M
authors.lastname: Tyers
authors.forename: Mark
authors.initials: M
authors.lastname: Goebl
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D000085962:Angiotensin-Converting Enzyme 2; D002453:Cell Cycle / Q000235:genetics; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000235:genetics* / Q000378:metabolism; D005813:Genes, Synthetic; D006207:Half-Life; D008969:Molecular Sequence Data; D007703:Peptidyl-Dipeptidase A / Q000235:genetics* / Q000378:metabolism; D025821:Polyubiquitin / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D050756:Cyclin-Dependent Kinase Inhibitor Proteins; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025821:Polyubiquitin; C577449:CDC34 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D007703:Peptidyl-Dipeptidase A; D000085962:Angiotensin-Converting Enzyme 2