Recombination and ligation of transfected DNA in CHO mutant EM9, which has high levels of sister chromatid exchange.

Transformation frequencies were measured in CHO mutant EM9 after transfection with intact or modified plasmid pSV2-gpt. The mutant and wild-type strain behaved similarly under all conditions except when homologous recombination was required to produce an intact plasmid. Therefore, the defect of the mutant which renders it slow in DNA strand break rejoining and high in sister chromatid exchange induction reduces its ability to recombine foreign DNA molecules.

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A CHO-cell strain having hypersensitivity to mutagens, a defect in DNA strand-break repair, and an extraordinary baseline frequency of sister-chromatid exchange

Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis ◽

10.1016/0027-5107(82)90276-7 ◽

1982 ◽

Vol 95 (2-3) ◽

pp. 427-440 ◽

Cited By ~ 208

Author(s):

L.H. Thompson ◽

K.W. Brookman ◽

L.E. Dillehay ◽

A.V. Carrano ◽

J.A. Mazrimas ◽

...

Keyword(s):

Sister Chromatid ◽

Sister Chromatid Exchange ◽

Strand Break ◽

Cell Strain ◽

Cho Cell ◽

Dna Strand Break ◽

Baseline Frequency ◽

Break Repair ◽

Dna Strand

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Mismatch Repair Proteins Regulate Heteroduplex Formation during Mitotic Recombination in Yeast

Molecular and Cellular Biology ◽

10.1128/mcb.18.11.6525 ◽

1998 ◽

Vol 18 (11) ◽

pp. 6525-6537 ◽

Cited By ~ 67

Author(s):

Wenliang Chen ◽

Sue Jinks-Robertson

Keyword(s):

Gene Conversion ◽

Mismatch Repair ◽

Sister Chromatid ◽

Type Strain ◽

Wild Type Strain ◽

Sequence Data ◽

Mitotic Recombination ◽

Assay System ◽

Wild Type ◽

Mmr Proteins

Mismatch repair (MMR) proteins actively inhibit recombination between diverged sequences in both prokaryotes and eukaryotes. Although the molecular basis of the antirecombination activity exerted by MMR proteins is unclear, it presumably involves the recognition of mismatches present in heteroduplex recombination intermediates. This recognition could be exerted during the initial stage of strand exchange, during the extension of heteroduplex DNA, or during the resolution of recombination intermediates. We previously used an assay system based on 350-bp inverted-repeat substrates to demonstrate that MMR proteins strongly inhibit mitotic recombination between diverged sequences inSaccharomyces cerevisiae. The assay system detects only those events that reverse the orientation of the region between the recombination substrates, which can occur as a result of either intrachromatid crossover or sister chromatid conversion. In the present study we sequenced the products of mitotic recombination between 94%-identical substrates in order to map gene conversion tracts in wild-type versus MMR-defective yeast strains. The sequence data indicate that (i) most recombination occurs via sister chromatid conversion and (ii) gene conversion tracts in an MMR-defective strain are significantly longer than those in an isogenic wild-type strain. The shortening of conversion tracts observed in a wild-type strain relative to an MMR-defective strain suggests that at least part of the antirecombination activity of MMR proteins derives from the blockage of heteroduplex extension in the presence of mismatches.

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Induction and repair of DNA strand breaks in Bacteroides fragilis

Canadian Journal of Microbiology ◽

10.1139/m90-085 ◽

1990 ◽

Vol 36 (7) ◽

pp. 490-494 ◽

Cited By ~ 1

Author(s):

Valerie R. Abratt ◽

Meyrick J. Peak ◽

Jennifer G. Peak ◽

Joseph D. Santangelo ◽

David R. Woods

Keyword(s):

Type Strain ◽

Wild Type Strain ◽

Bacteroides Fragilis ◽

Wild Type ◽

Anaerobic Conditions ◽

Sensitive Mutant ◽

Strand Breaks ◽

In The Wild ◽

Strand Breakage ◽

Dna Strand

Alkaline sucrose gradient sedimentation was used to establish whether strand breakage and repair take place in the DNA of UV-irradiated Bacteroides fragilis during the removal of pyrimidine dimers. A B. fragilis wild-type strain and two of its repair mutants, a mitomycin C sensitive mutant (MTC25) having wild-type levels of UV survival, and a UV-sensitive, mitomycin C sensitive mutant (UVS9), were investigated. Under anaerobic conditions, far-UV irradiation induced metabolically regulated strand breakage and resynthesis in the wild-type strain, but this was markedly reduced in both the MTC25 and UVS9 mutants. Approximately half of the strand breaks generated by the various strains were rejoined during further holding in buffer. Under replicating conditions, complete repair of strand breaks in the wild type was observed. Caffeine treatment under anaerobic conditions caused direct DNA strand breakage in B. fragilis cells but did not inhibit UV-induced breakage or repair. Key words: Bacteroides fragilis, DNA breakage, DNA repair, caffeine.

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Cooperative Roles of Vertebrate Fbh1 and Blm DNA Helicases in Avoidance of Crossovers during Recombination Initiated by Replication Fork Collapse

Molecular and Cellular Biology ◽

10.1128/mcb.02043-06 ◽

2007 ◽

Vol 27 (8) ◽

pp. 2812-2820 ◽

Cited By ~ 30

Author(s):

Masaoki Kohzaki ◽

Atsushi Hatanaka ◽

Eiichiro Sonoda ◽

Mitsuyoshi Yamazoe ◽

Koji Kikuchi ◽

...

Keyword(s):

Homologous Recombination ◽

Sister Chromatid ◽

Sister Chromatid Exchange ◽

Replication Fork ◽

Strand Break ◽

Dna Helicase ◽

Dna Helicases ◽

Homologous Chromosomes ◽

Dna Damaging Agents ◽

Replication Fork Arrest

ABSTRACT Fbh1 (F-box DNA helicase 1) orthologues are conserved from Schizosaccharomyces pombe to chickens and humans. Here, we report the disruption of the FBH1 gene in DT40 cells. Although the yeast fbh1 mutant shows an increase in sensitivity to DNA damaging agents, FBH1 − / − DT40 clones show no prominent sensitivity, suggesting that the loss of FBH1 might be compensated by other genes. However, FBH1 − / − cells exhibit increases in both sister chromatid exchange and the formation of radial structures between homologous chromosomes without showing a defect in homologous recombination. This phenotype is reminiscent of BLM − / − cells and suggests that Fbh1 may be involved in preventing extensive strand exchange during homologous recombination. In addition, disruption of RAD54, a major homologous recombination factor in FBH1 − / − cells, results in a marked increase in chromosome-type breaks (breaks on both sister chromatids at the same place) following replication fork arrest. Further, FBH1 BLM cells showed additive increases in both sister chromatid exchange and the formation of radial chromosomes. These data suggest that Fbh1 acts in parallel with Bloom helicase to control recombination-mediated double-strand-break repair at replication blocks and to reduce the frequency of crossover.

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Involvement of a periplasmic protein kinase in DNA strand break repair and homologous recombination in Escherichia coli

Molecular Microbiology ◽

10.1111/j.1365-2958.2007.05919.x ◽

2007 ◽

Vol 65 (6) ◽

pp. 1595-1595

Author(s):

Nivedita P. Khairnar ◽

Vidya A. Kamble ◽

Suhas H. Mangoli ◽

Shree K. Apte ◽

Hari S. Misra

Keyword(s):

Escherichia Coli ◽

Protein Kinase ◽

Homologous Recombination ◽

Strand Break ◽

Periplasmic Protein ◽

Dna Strand Break ◽

Break Repair ◽

Dna Strand

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The cohesion protein ORD is required for homologue bias during meiotic recombination

The Journal of Cell Biology ◽

10.1083/jcb.200310077 ◽

2004 ◽

Vol 164 (6) ◽

pp. 819-829 ◽

Cited By ~ 56

Author(s):

Hayley A. Webber ◽

Louisa Howard ◽

Sharon E. Bickel

Keyword(s):

Electron Microscopy ◽

Homologous Recombination ◽

Sister Chromatid ◽

Meiotic Recombination ◽

Sister Chromatid Exchange ◽

Ring Chromosome ◽

Double Strand Breaks ◽

Wild Type ◽

Strand Breaks ◽

Chromatid Cohesion

During meiosis, sister chromatid cohesion is required for normal levels of homologous recombination, although how cohesion regulates exchange is not understood. Null mutations in orientation disruptor (ord) ablate arm and centromeric cohesion during Drosophila meiosis and severely reduce homologous crossovers in mutant oocytes. We show that ORD protein localizes along oocyte chromosomes during the stages in which recombination occurs. Although synaptonemal complex (SC) components initially associate with synapsed homologues in ord mutants, their localization is severely disrupted during pachytene progression, and normal tripartite SC is not visible by electron microscopy. In ord germaria, meiotic double strand breaks appear and disappear with frequency and timing indistinguishable from wild type. However, Ring chromosome recovery is dramatically reduced in ord oocytes compared with wild type, which is consistent with the model that defects in meiotic cohesion remove the constraints that normally limit recombination between sisters. We conclude that ORD activity suppresses sister chromatid exchange and stimulates inter-homologue crossovers, thereby promoting homologue bias during meiotic recombination in Drosophila.

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Involvement of a periplasmic protein kinase in DNA strand break repair and homologous recombination in Escherichia coli

Molecular Microbiology ◽

10.1111/j.1365-2958.2007.05779.x ◽

2007 ◽

Vol 65 (2) ◽

pp. 294-304 ◽

Cited By ~ 22

Author(s):

Nivedita P. Khairnar ◽

Vidya A. Kamble ◽

Suhas H. Mangoli ◽

Shree K. Apte ◽

Hari S. Misra

Keyword(s):

Escherichia Coli ◽

Protein Kinase ◽

Homologous Recombination ◽

Strand Break ◽

Periplasmic Protein ◽

Dna Strand Break ◽

Break Repair ◽

Dna Strand

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Mutations in Homologous Recombination Genes Rescue top3 Slow Growth in Saccharomyces cerevisiae

Genetics ◽

10.1093/genetics/162.2.647 ◽

2002 ◽

Vol 162 (2) ◽

pp. 647-662 ◽

Cited By ~ 2

Author(s):

Erika Shor ◽

Serge Gangloff ◽

Marisa Wagner ◽

Justin Weinstein ◽

Gavrielle Price ◽

...

Keyword(s):

Homologous Recombination ◽

Type Strain ◽

Wild Type Strain ◽

Slow Growth ◽

Recq Helicase ◽

Wild Type ◽

Growth Defects ◽

Topoisomerase Iii ◽

Hyper Sensitivity ◽

Instability Phenotype

Abstract In budding yeast, loss of topoisomerase III, encoded by the TOP3 gene, leads to a genomic instability phenotype that includes slow growth, hyper-sensitivity to genotoxic agents, mitotic hyper-recombination, increased chromosome missegregation, and meiotic failure. Slow growth and other defects of top3 mutants are suppressed by mutation of SGS1, which encodes the only RecQ helicase in S. cerevisiae. sgs1 is epistatic to top3, suggesting that the two proteins act in the same pathway. To identify other factors that function in the Sgs1-Top3 pathway, we undertook a genetic screen for non-sgs1 suppressors of top3 defects. We found that slow growth and DNA damage sensitivity of top3 mutants are suppressed by mutations in RAD51, RAD54, RAD55, and RAD57. In contrast, top3 mutants show extreme synergistic growth defects with mutations in RAD50, MRE11, XRS2, RDH54, and RAD1. We also analyzed recombination at the SUP4-o region, showing that in a rad51, rad54, rad55, or rad57 background top3Δ does not increase recombination to the same degree as in a wild-type strain. These results suggest that the presence of the Rad51 homologous recombination complex in a top3 background facilitates creation of detrimental intermediates by Sgs1. We present a model wherein Rad51 helps recruit Sgs1-Top3 to sites of replicative damage.

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The Critical Role of Polyketide Synthase Gene On The Swainsonine Biosynthesis in The Fungus Metarhizium Anisopliae

10.21203/rs.3.rs-1092840/v1 ◽

2021 ◽

Author(s):

Lu Sun ◽

Enxia Huang ◽

Yu Zhang ◽

Ziyu Guo ◽

Kexin Wu ◽

...

Keyword(s):

Homologous Recombination ◽

Metarhizium Anisopliae ◽

Type Strain ◽

Polyketide Synthase ◽

Wild Type Strain ◽

Biosynthesis Pathway ◽

Wild Type ◽

Knock Out ◽

Polyketide Synthase Gene

Abstract Swainsonine (SW) is the principal toxic ingredient of locoweeds, and is produced by fungi including Metarhizium anisopliae, Slafractonia leguminicola, and Alternaria oxytropis. While the SW biosynthesis pathway of fungi and the catalytic enzyme genes that regulate synthesis are not cleanly. In this study, we used homologous recombination (HR) to knock out and interfere with the polyketide synthase gene (pks) of M. anisopliae to determine its effect on the SW biosynthesis pathway. The concentration of SW was measured in the fermentation broth of M. anisopliae at 1 d, 2 d, 3 d, 4 d, 5 d, 6 d or 7 d using LC-MS. The gene for the pks gene was detected by RT-qPCR. Day 5 of M. anisopliae gave the highest content of SW and the highest expression of the pks gene. To determine the role of the pks gene in the SW biosynthesis pathway of M. anisopliae, we used PEG-mediated homologous recombination (HR) to transform a wild-type strain (WT) with a Benomyl (ben)-resistant fragment to knock out the pks gene producing a mutant-type strain (MT) and used PEG-mediated RNAi to transform a wild-type strain (WT) with a Benomyl (ben)-resistant plasmid to interfere with the pks gene. A complemented-type (CT) strain was produced by adding a complementation vector that contains the geneticin (G418) resistance gene as a marker. The content of SW didn’t detected in MT strain, and returned to the original level in the CT strain, while the content of SW was significantly decreased in RNAi strain. We suggest that mutation and RNAi in the pks gene affect the cell wall formation of M. anisopliae, while the colony diameters, phenotypes, and growth rates did not change significantly, and no obvious changes in other cellular organelles were noted. These results indicate that the pks gene plays a crucial role in the SW biosynthesis of M. anisopliae, which provides an important theoretical basis for illuminating the SW biosynthesis and solving locoism in livestock.

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