title: Caenorhabditis elegans UBC-1, a ubiquitin-conjugating enzyme homologous to yeast RAD6/UBC2, contains a novel carboxy-terminal extension that is conserved in nematodes.
abstract: The RAD6/UBC2 gene from Saccharomyces cerevisiae encodes a ubiquitin-conjugating enzyme involved in DNA repair, induced mutagenesis, and sporulation. Here we report the isolation and characterization of the Caenorhabditis elegans RAD6 homolog designated ubc-1. Ubc-1 encodes a 21.5-kD protein that shares considerable identity with RAD6 (66%) as well as with other RAD6 homologs, including Schizosaccharomyces pombe rhp6+ (70%), Drosophila melanogaster Dhr6 (83%), and the two human homologs HHR6A and HHR6B (84% and 83%, respectively). However, UBC-1 is distinct in being the only known RAD6 homolog, other than RAD6 itself, with a carboxy-terminal extension. Analysis of UBC-1 homologs from C. briggsae and Ascaris suum show that the presence of the carboxy-terminal extension is conserved in nematodes. When constitutively expressed from the yeast promoter ADH1, ubc-1 complements the DNA repair functions in a S. cerevisiae rad6 delta mutant. Surprisingly, ubc-1 fails to complement the sporulation function of RAD6, despite its possession of an acidic carboxy-terminal tail. C. elegans UBC-1 is capable of forming a thiol-ester bond with ubiquitin, but, unlike RAD6, is unable to transfer ubiquitin to histone H2B in vitro. Both cis and trans splicing are involved in the maturation of the ubc-1 transcript. The presence of the SL2 trans-splice leader in the ubc-1 transcript suggests that ubc-1 may be co-transcribed as part of a polycistronic message.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada.
authors.forename: D S
authors.initials: DS
authors.lastname: Leggett
authors.forename: D
authors.initials: D
authors.lastname: Jones
authors.forename: E P
authors.initials: EP
authors.lastname: Candido
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001200:Ascaris / Q000737:chemistry; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins; D004331:Drosophila melanogaster / Q000737:chemistry; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D005800:Genes, Fungal; D017238:Genes, Helminth; D005816:Genetic Complementation Test; D015801:Helminth Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D006801:Humans; D008025:Ligases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D012326:RNA Splicing; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D044763:Ubiquitin-Conjugating Enzymes; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D005656:Fungal Proteins; D015801:Helminth Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; C471606:RAD6 protein, S cerevisiae; C066752:UBC1 protein, S cerevisiae; C471545:UBE2A protein, human; C471546:UBE2B protein, human; D044763:Ubiquitin-Conjugating Enzymes; C489359:ubc-1 protein, C elegans; D008025:Ligases