Homologous Recombination and DNA-End Joining Reactions in Zygotes and Early Embryos of Zebrafish (Danio rerio) and Drosophila melanogaster

ABSTRACT The Saccharomyces cerevisiae Srs2 protein is involved in DNA repair and recombination. In order to gain better insight into the roles of Srs2, we performed a screen to identify mutations that are synthetically lethal with an srs2 deletion. One of them is a mutated allele of the ULP1 gene that encodes a protease specifically cleaving Smt3-protein conjugates. This allele, ulp1-I615N, is responsible for an accumulation of Smt3-conjugated proteins. The mutant is unable to grow at 37°C. At permissive temperatures, it still shows severe growth defects together with a strong hyperrecombination phenotype and is impaired in meiosis. Genetic interactions between ulp1 and mutations that affect different repair pathways indicated that the RAD51-dependent homologous recombination mechanism, but not excision resynthesis, translesion synthesis, or nonhomologous end-joining processes, is required for the viability of the mutant. Thus, both Srs2, believed to negatively control homologous recombination, and the process of recombination per se are essential for the viability of the ulp1 mutant. Upon replication, mutant cells accumulate single-stranded DNA interruptions. These structures are believed to generate different recombination intermediates. Some of them are fixed by recombination, and others require Srs2 to be reversed and fixed by an alternate pathway.

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Specificity of Chromosome Damage Caused by the Rex Element of Drosophila melanogaster

Genetics ◽

10.1093/genetics/144.1.109 ◽

1996 ◽

Vol 144 (1) ◽

pp. 109-115 ◽

Cited By ~ 1

Author(s):

Leonard G Robbins

Keyword(s):

Drosophila Melanogaster ◽

Early Development ◽

X Chromosome ◽

Ribosomal Rna ◽

Chromosome Damage ◽

Genetic Element ◽

Single Chromosome ◽

Experimental Cross ◽

Rdna Array ◽

Early Embryos

Abstract Rex is a multicopy genetic element that maps within an X-linked ribosomal RNA gene (rDNA) array of D. melanogaster. Acting maternally, Rex causes recombination between rDNA arrays in a few percent of early embryos. With target chromosomes that contain two rDNA arrays, the exchanges either delete all of the material between the two arrays or invert the entire intervening chromosomal segment. About a third of the embryos produced by Rex homozygotes have cytologically visible chromosome damage, nearly always involving a single chromosome. Most of these embryos die during early development, displaying a characteristic apoptosis-like phenotype. An experiment that tests whether the cytologically visible damage is rDNA-specific is reported here. In this experiment, females heterozygous for Rex and an rDNA-deficient X chromosome were crossed to males of two genotypes. Some of the progeny from the experimental cross entirely lacked rDNA, while all of the progeny from the control cross had at least one rDNA array. A significantly lower frequency of early-lethal embryos in the experimental cross, proportionate to the fraction of rDNA-deficient embryos, demonstrates that Rex preferentially damages rDNA.

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The effect of Hus1 on ionizing radiation sensitivity is associated with homologous recombination repair but is independent of nonhomologous end-joining

Oncogene ◽

10.1038/sj.onc.1209212 ◽

2005 ◽

Vol 25 (13) ◽

pp. 1980-1983 ◽

Cited By ~ 20

Author(s):

X Wang ◽

B Hu ◽

R S Weiss ◽

Y Wang

Keyword(s):

Homologous Recombination ◽

Ionizing Radiation ◽

Radiation Sensitivity ◽

Nonhomologous End Joining ◽

Homologous Recombination Repair ◽

End Joining ◽

Recombination Repair

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Identification and isolation of a BTB–POZ-containing gene expressed in oocytes and early embryos of the zebrafish Danio rerio

Genome ◽

10.1139/g06-041 ◽

2006 ◽

Vol 49 (7) ◽

pp. 808-814

Author(s):

T H.L Smith ◽

K Stedronsky ◽

B Morgan ◽

R A McGowan

Keyword(s):

Expression Pattern ◽

Danio Rerio ◽

Early Cleavage ◽

Genes Expression ◽

Early Embryos

In this report, we describe the cloning of a cDNA from the zebrafish Danio rerio encoding a protein containing a BTB–POZ domain closely resembling the BTBD1 and BTBD2 proteins previously identified in mammals. However, unlike other BTB–POZ-containing genes, expression of this gene in adults is most abundant in oocytes, where the RNA can be detected at all stages of oogenesis examined. The presence of the RNA persists through early cleavage, but is decreased significantly by gastrulation. Although the function of this gene has yet to be determined, its resemblance to the BTB–POZ family of genes coupled with its expression pattern suggests that it may have an important function in oogenesis and (or) early zebrafish development.Key words: BTBD1, BTBD2, BTB–POZ domain, kelch superfamily, PHR domain.

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Ku Heterodimer-Independent End Joining in Trypanosoma brucei Cell Extracts Relies upon Sequence Microhomology

Eukaryotic Cell ◽

10.1128/ec.00212-07 ◽

2007 ◽

Vol 6 (10) ◽

pp. 1773-1781 ◽

Cited By ~ 38

Author(s):

Peter Burton ◽

David J. McBride ◽

Jonathan M. Wilkes ◽

J. David Barry ◽

Richard McCulloch

Keyword(s):

Homologous Recombination ◽

Trypanosoma Brucei ◽

Antigenic Variation ◽

Bacterial Species ◽

Nonhomologous End Joining ◽

Dna Double Strand Breaks ◽

End Joining ◽

Strand Breaks ◽

Cell Extracts ◽

Ligase Iv

ABSTRACT DNA double-strand breaks (DSBs) are repaired primarily by two distinct pathways: homologous recombination and nonhomologous end joining (NHEJ). NHEJ has been found in all eukaryotes examined to date and has been described recently for some bacterial species, illustrating its ancestry. Trypanosoma brucei is a divergent eukaryotic protist that evades host immunity by antigenic variation, a process in which homologous recombination plays a crucial function. While homologous recombination has been examined in some detail in T. brucei, little work has been done to examine what other DSB repair pathways the parasite utilizes. Here we show that T. brucei cell extracts support the end joining of linear DNA molecules. These reactions are independent of the Ku heterodimer, indicating that they are distinct from NHEJ, and are guided by sequence microhomology. We also demonstrate bioinformatically that T. brucei, in common with other kinetoplastids, does not encode recognizable homologues of DNA ligase IV or XRCC4, suggesting that NHEJ is either absent or mechanistically diverged in these pathogens.

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Deletion of the DNA Ligase IV Gene in Candida glabrata Significantly Increases Gene-Targeting Efficiency

Eukaryotic Cell ◽

10.1128/ec.00281-14 ◽

2015 ◽

Vol 14 (8) ◽

pp. 783-791 ◽

Cited By ~ 5

Author(s):

Yuke Cen ◽

Alessandro Fiori ◽

Patrick Van Dijck

Keyword(s):

Homologous Recombination ◽

Gene Targeting ◽

Candida Glabrata ◽

The United States ◽

Genetic Alterations ◽

Nonhomologous End Joining ◽

Specific Gene ◽

Phylogenetic Distance ◽

End Joining ◽

Content Type

ABSTRACTCandida glabratais reported as the second most prevalent human opportunistic fungal pathogen in the United States. Over the last decades, its incidence increased, whereas that ofCandida albicansdecreased slightly. One of the main reasons for this shift is attributed to the inherent tolerance ofC. glabratatoward the commonly used azole antifungal drugs. Despite a close phylogenetic distance toSaccharomyces cerevisiae, homologous recombination works with poor efficiency inC. glabratacompared to baker's yeast, in fact limiting targeted genetic alterations of the pathogen's genome. It has been shown that nonhomologous DNA end joining is dominant over specific gene targeting inC. glabrata. To improve the homologous recombination efficiency, we have generated a strain in which theLIG4gene has been deleted, which resulted in a significant increase in correct gene targeting. The very specific function of Lig4 in mediating nonhomologous end joining is the reason for the absence of clear side effects, some of which affect theku80mutant, another mutant with reduced nonhomologous end joining. We also generated aLIG4reintegration cassette. Our results show that thelig4mutant strain may be a valuable tool for theC. glabrataresearch community.

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Proton Irradiation Increases the Necessity for Homologous Recombination Repair Along with the Indispensability of Non-Homologous End Joining

Cells ◽

10.3390/cells9040889 ◽

2020 ◽

Vol 9 (4) ◽

pp. 889 ◽

Cited By ~ 3

Author(s):

Klaudia Szymonowicz ◽

Adam Krysztofiak ◽

Jansje van der Linden ◽

Ajvar Kern ◽

Simon Deycmar ◽

...

Keyword(s):

Dna Damage ◽

Homologous Recombination ◽

Proton Irradiation ◽

Negative Impact ◽

Particle Therapy ◽

Homologous Recombination Repair ◽

End Joining ◽

X Ray ◽

Recombination Repair ◽

Non Homologous End Joining

Technical improvements in clinical radiotherapy for maximizing cytotoxicity to the tumor while limiting negative impact on co-irradiated healthy tissues include the increasing use of particle therapy (e.g., proton therapy) worldwide. Yet potential differences in the biology of DNA damage induction and repair between irradiation with X-ray photons and protons remain elusive. We compared the differences in DNA double strand break (DSB) repair and survival of cells compromised in non-homologous end joining (NHEJ), homologous recombination repair (HRR) or both, after irradiation with an equal dose of X-ray photons, entrance plateau (EP) protons, and mid spread-out Bragg peak (SOBP) protons. We used super-resolution microscopy to investigate potential differences in spatial distribution of DNA damage foci upon irradiation. While DNA damage foci were equally distributed throughout the nucleus after X-ray photon irradiation, we observed more clustered DNA damage foci upon proton irradiation. Furthermore, deficiency in essential NHEJ proteins delayed DNA repair kinetics and sensitized cells to both, X-ray photon and proton irradiation, whereas deficiency in HRR proteins sensitized cells only to proton irradiation. We assume that NHEJ is indispensable for processing DNA DSB independent of the irradiation source, whereas the importance of HRR rises with increasing energy of applied irradiation.

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TIP60 K430 SUMOylation attenuates its interaction with DNA-PKcs in S-phase cells: Facilitating homologous recombination and emerging target for cancer therapy

Science Advances ◽

10.1126/sciadv.aba7822 ◽

2020 ◽

Vol 6 (28) ◽

pp. eaba7822 ◽

Cited By ~ 1

Author(s):

Shan-Shan Gao ◽

Hua Guan ◽

Shuang Yan ◽

Sai Hu ◽

Man Song ◽

...

Keyword(s):

Cancer Therapy ◽

Homologous Recombination ◽

Cellular Response ◽

Parp Inhibitors ◽

S Phase ◽

Tumor Growth Inhibition ◽

Dna Double Strand Breaks ◽

End Joining ◽

Pathway Activation ◽

Pathway Choice

Nonhomologous end joining (NHEJ) and homologous recombination (HR) are major repair pathways of DNA double-strand breaks (DSBs). The pathway choice of HR and NHEJ is tightly regulated in cellular response to DNA damage. Here, we demonstrate that the interaction of TIP60 with DNA-PKcs is attenuated specifically in S phase, which facilitates HR pathway activation. SUMO2 modification of TIP60 K430 mediated by PISA4 E3 ligase blocks its interaction with DNA-PKcs, whereas TIP60 K430R mutation recovers its interaction with DNA-PKcs, which results in abnormally increased phosphorylation of DNA-PKcs S2056 in S phase and marked inhibition of HR efficiency, but barely affects NHEJ activity. TIP60 K430R mutant cancer cells are more sensitive to radiation and PARP inhibitors in cancer cell killing and tumor growth inhibition. Collectively, coordinated regulation of TIP60 and DNA-PKcs facilitates HR pathway choice in S-phase cells. TIP60 K430R mutant is a potential target of radiation and PARPi cancer therapy.

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