title: Elevated Genome-Wide Instability in Yeast Mutants Lacking RNase H Activity.
abstract: Two types of RNA:DNA associations can lead to genome instability: the formation of R-loops during transcription and the incorporation of ribonucleotide monophosphates (rNMPs) into DNA during replication. Both ribonuclease (RNase) H1 and RNase H2 degrade the RNA component of R-loops, whereas only RNase H2 can remove one or a few rNMPs from DNA. We performed high-resolution mapping of mitotic recombination events throughout the yeast genome in diploid strains of Saccharomyces cerevisiae lacking RNase H1 (rnh1Δ), RNase H2 (rnh201Δ), or both RNase H1 and RNase H2 (rnh1Δ rnh201Δ). We found little effect on recombination in the rnh1Δ strain, but elevated recombination in both the rnh201Δ and the double-mutant strains; levels of recombination in the double mutant were ∼50% higher than in the rnh201 single-mutant strain. An rnh201Δ mutant that additionally contained a mutation that reduces rNMP incorporation by DNA polymerase ε (pol2-M644L) had a level of instability similar to that observed in the presence of wild-type Pol ε. This result suggests that the elevated recombination observed in the absence of only RNase H2 is primarily a consequence of R-loops rather than misincorporated rNMPs.
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina 27710.
authors.forename: Karen
authors.initials: K
authors.lastname: O'Connell
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina 27710 tom.petes@duke.edu sue.robertson@duke.edu.
authors.forename: Sue
authors.initials: S
authors.lastname: Jinks-Robertson
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina 27710 tom.petes@duke.edu sue.robertson@duke.edu.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Petes
mesh_terms: D015825:Chromosomes, Fungal; D004261:DNA Replication; D004271:DNA, Fungal / Q000378:metabolism; D042822:Genomic Instability; D019656:Loss of Heterozygosity; D009154:Mutation; D009690:Nucleic Acid Conformation; D012331:RNA, Fungal / Q000378:metabolism; D011995:Recombination, Genetic; D016914:Ribonuclease H / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D004271:DNA, Fungal; D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D012260:Ribonucleases; C569437:Rnh201 protein, S cerevisiae; D016914:Ribonuclease H; C078856:ribonuclease HI
keywords: RNase H1; RNase H2; loss of heterozygosity; microarrays; mitotic recombination