title: A hyper-recombination mutation in S. cerevisiae identifies a novel eukaryotic topoisomerase.
abstract: A hyper-recombination mutation was isolated that causes an increase in recombination between short repeated delta sequences surrounding the SUP4-omicron gene in S. cerevisiae. The wild-type copy of this gene was cloned by complementation of one of its pleiotropic phenotypes, slow growth. DNA sequence of the clone revealed a 656 amino acid open reading frame capable of encoding a protein homologous to the bacterial type I topoisomerase. No homology was detected with previously identified eukaryotic topoisomerases. Construction of double mutants with either of the two known yeast topoisomerase genes revealed synergistic effects on growth suggesting overlapping functions. Expression of bacterial topoisomerase I in yeast can fully complement the slow growth defect of a null mutation. We have named this locus TOP3 and suggest that it defines a novel eukaryotic topoisomerase gene.
authors.affiliation: Department of Genetics and Development, Columbia University College of Physicians and Surgeons, New York, New York 10032.
authors.forename: J W
authors.initials: JW
authors.lastname: Wallis
authors.forename: G
authors.initials: G
authors.lastname: Chrebet
authors.forename: G
authors.initials: G
authors.lastname: Brodsky
authors.forename: M
authors.initials: M
authors.lastname: Rolfe
authors.forename: R
authors.initials: R
authors.lastname: Rothstein
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D004247:DNA / Q000032:analysis / Q000235:genetics; D004264:DNA Topoisomerases, Type I / Q000032:analysis / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004926:Escherichia coli; D008040:Genetic Linkage; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D004247:DNA; D004264:DNA Topoisomerases, Type I