title: Conserved function of RNF4 family proteins in eukaryotes: targeting a ubiquitin ligase to SUMOylated proteins.
abstract: The function of small ubiquitin-like modifier (SUMO)-binding proteins is key to understanding how SUMOylation regulates cellular processes. We identified two related Schizosaccharomyces pombe proteins, Rfp1 and Rfp2, each having an N-terminal SUMO-interacting motif (SIM) and a C-terminal RING-finger domain. Genetic analysis shows that Rfp1 and Rfp2 have redundant functions; together, they are essential for cell growth and genome stability. Mammalian RNF4, an active ubiquitin E3 ligase, is an orthologue of Rfp1/Rfp2. Rfp1 and Rfp2 lack E3 activity but recruit Slx8, an active RING-finger ubiquitin ligase, through a RING-RING interaction, to form a functional E3. RNF4 complements the growth and genomic stability defects of rfp1rfp2, slx8, and rfp1rfp2slx8 mutant cells. Both the Rfp-Slx8 complex and RNF4 specifically ubiquitylate artificial SUMO-containing substrates in vitro in a SUMO binding-dependent manner. SUMOylated proteins accumulate in rfp1rfp2 double-null cells, suggesting that Rfp/Slx8 proteins may promote ubiquitin-dependent degradation of SUMOylated targets. Hence, we describe a family of SIM-containing RING-finger proteins that potentially regulates eukaryotic genome stability through linking SUMO-interaction with ubiquitin conjugation.
authors.affiliation: Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Sun
authors.forename: Joel D
authors.initials: JD
authors.lastname: Leverson
authors.forename: Tony
authors.initials: T
authors.lastname: Hunter
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins; D005057:Eukaryotic Cells / Q000378:metabolism*; D019143:Evolution, Molecular; D042822:Genomic Instability; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C524067:Rpf1 protein, S pombe; C524068:Rpf2 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D014157:Transcription Factors; D025801:Ubiquitin; C486410:Rnf4 protein, mouse; C587431:Slx8 protein, S pombe; D044767:Ubiquitin-Protein Ligases