HPR1, a novel yeast gene that prevents intrachromosomal excision recombination, shows carboxy-terminal homology to the Saccharomyces cerevisiae TOP1 gene.

The HPR1 gene has been cloned by complementation of the hyperrecombination phenotype of hpr1-1 strains by using a color assay system. HPR1 is a gene that is in single copy on chromosome IV of Saccharomyces cerevisiae, closely linked to ARO1, and it codes for a putative protein of 752 amino ...
acids (molecular mass, 88 kilodaltons). Computer searches revealed homology (48.8% conserved homology; 24.8% identity) with the S. cerevisiae TOP1 gene in an alpha-helical stretch of 129 amino acids near the carboxy-terminal region of both proteins. The ethyl methanesulfonate-induced hpr1-1 mutation is a single-base change that produces a stop codon at amino acid 559 coding for a protein that lacks the carboxy-terminal TOP1 homologous region. Haploid strains carrying deletions of the HPR1 gene show a slightly reduced mitotic growth rate and extremely high rates of intrachromosomal excision recombination (frequency, 10 to 15%) but have a undetectable effect on rDNA recombination. Double-null mutants hpr1 top1 grow very poorly. We conclude that Hpr1 is a novel eucaryotic protein, mutation of which causes an increase in mitotic intrachromosomal excision recombination, and that it may be functionally related to an activity of the topoisomerase I protein.
Mesh Terms:
Alleles, Amino Acid Sequence, Base Sequence, Chromosomes, Fungal, Cloning, Molecular, DNA, Fungal, DNA, Ribosomal, Fungal Proteins, Genes, Fungal, Genetic Complementation Test, Genotype, Molecular Sequence Data, Mutation, Nuclear Proteins, Plasmids, RNA, Fungal, Recombination, Genetic, Restriction Mapping, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Homology, Nucleic Acid
Mol. Cell. Biol.
Date: Apr. 01, 1990
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