Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Recombinational DNA Repair”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2025

WDFY2 promotes MRN complex formation required for homologous recombination-mediated DNA repair.

The MRE11-RAD50-NBS1 (MRN) complex is fundamental for detecting and repairing DNA double-strand breaks (DSBs), thereby safeguarding genome integrity. However, the precise mechanism governing MRN complex recruitment to DSBs remains largely unexplored. Here, we identify WD40- and FYVE domain-containing protein 2 (WDFY2) as an important regulator of MRN complex formation at DNA damage sites, facilitating homologous recombination (HR) repair. Mechanistically, WDFY2 is phosphorylated at serine 84 by the ATM-CHK2 axis, priming it for recruitment to DSBs. Through direct interactions with MRE11 and NBS1, WDFY2 bridges the MRE11-RAD50 subcomplex with NBS1, thereby promoting MRN complex formation at DSBs and DNA end resection. WDFY2 deficiency, as well as the non-phosphorylatable S84A mutant, results in impaired HR repair and reduced cell survival following DNA damage. Collectively, our findings establish WDFY2 as a key platform for MRN complex loading at DSBs and HR repair, highlighting it as a potential therapeutic target for cancer treatment.

Humans↗
PubMed1978

Cell-cycle variation in the induction of lethality and mitotic recombination after treatment with UV and nitrous acid in the yeast, Saccharomyces cerevisiae.

Exponentially growing yeast cultures separated into discrete periods of the cell cycle by zonal rotor centrifugation show cyclic variation in both UV and nitrous acid induced cell lethality, mitotic gene conversion and mitotic crossing-over. Maximum cell survival after UV treatment was observed in the S and G2 phases of the cell cycle at a time when UV induction of both types of mitotic recombination was at a minimum. In contrast, cell inactivation by the chemical mutagen nitrous acid showed a single discrete period of sensitivity which occurred in S phase cells which are undergoing DNA synthesis. Mitotic gene conversion and mitotic crossing-over were induced by nitrous acid in cells at all stages of the cell cycle with a peak of induction of both events occurring at the time of maximum cell lethality. The lack of correlation observed between maximum cell and the maximum induction of mitotic intragenic recombination suggest that other DNA-repair mechanisms besides DNA-recombination repair are involved in the recovery of inactivated yeast cells during the cell cycle.

Cell Cycle↗
PubMed1979

Effect of mutagens, chemotherapeutic agents and defects in DNA repair genes on recombination in F' partial diploid Escherichia coli.

The ability of mutagenic agents, nonmutagenic substances and defects in DNA repair to alter the genotype of F' partial diploid (F30) Escherichia coli was determined. The frequency of auxotrophic mutants and histidine requiring (His-) haploid colonies was increased by mutagen treatment but Hfr colonies were not detected in F30 E. coli even with specific selection techniques. Genotype changes due to nonreciprocal recombination were determined by measuring the frequency of His- homogenotes, eg. F' hisC780, hisI+/hisC780, hisI+, arising from a His+ heterogenote, F' hisC780 hisI+/hisC+, his1903. At least 75% of the recombinants were homozygous for histidine alleles which were present on the F' plasmid (exogenote) of the parental hetergenote rather than for histidine alleles on the chromosome. Mutagens, chemotherapeutic agents which histidine alleles on the chromosome. Mutagens, chemotherapeutic agents which block DNA synthesis and a defective DNA polymerase I gene, polA1, were found to increase the frequency of nonreciprocal recombination. A defect in the ability to excise thymine dimers, uvrC34, did not increase spontaneous nonreciprocal recombination. However, UV irradiation but not methyl methanesulfonate (MMS) induced greater recombination in this excision-repair defective mutant than in DNA-repair-proficient strains. Mutagenic agents, with the exception of ethyl methanesulfonate (EMS), induced greater increases in recombination than the chemotherapeutic agents or the polA1 mutation. EMS, which causes relatively little degradation of DNA, was more mutagenic but less recombinogenic than MMS, a homologous compound ths that inhibition of DNA occurring single-stranded regions in replicative intermediates of the DNA. Mutagens which cause the rapid breakdown of DNA may, in addition, introduce lesions into the genome that increase the number of single-stranded regions thus inducing even higher frequencies of recombination.

Antimetabolites↗
PubMed1979

Molecular recombination and the repair of DNA double-strand breaks in CHO cells.

Molecular recombination and the repair of DNA double-strand breaks (DSB) have been examined in the G-0 and S phase of the cell cycle using a temperature-sensitive CHO cell line to test i) if there are cell cycle restrictions on the repair of DSB's' ii) the extent to which molecular recombination can be induced between either sister chromatids or homologous chromosomes and iii) whether repair of DSB's involves recombination (3). Mitomycin C (1-2 micrograms/ml) or ionizing radiation (50 krad) followed by incubation resulted in molecular recombination (hybrid DNA) in S phase cells. Approximately 0.03 to 0.10% of the molecules (number average molecular weight: 5.6 x 10(6) Daltons after shearing) had hybrid regions for more than 75% of their length. However, no recombination was detected in G-0 cells. Since the repair of DSB was observed in both stages with more than 50% of the breaks repaired in 5 hours, it appears that DSB repair in G-0 cells does not involve recombination between homologous chromosomes. The possibility is not excluded that repair in G-0 cells involves only small regions (less than 4 x 10(6) Daltons).

Animals↗
PubMed1978

Antagonists of DNA gyrase inhibit repair and recombination of UV-irradiated phage lambda.

Intracellular lambda DNA (from EDTA-sensitive tandem duplication phages) was extracted from infected rec+ bacteria and scored for infectivity and recombination (loss of duplication) by transfection of recA recB spheroplasts and subsequent assay for EDTA resistance. When phage development was blocked by repressor or by antibiotics (chloramphenicol and/or rifampin), the apparent recombination frequency was about 0.1% above the background value for recA infections. Prior irradiation of the phage greatly stimulated recombination; the frequency was 20% when UV fluence was 140 J/m2. Repair (recovery of infectivity) and recombination of irradiated phage DNA proceeded readily in the presence of chloramphenicol and rifampin. Inhibitors of DNA gyrase (coumermycin and oxolinic acid) blocked repair and reduced recombination. UV-stimulated recombination was very low in recA but nearly normal in recB cells: repair was reduced in both mutant strains. The recombination remained high as phage/cell ratios less than unity.

Aminocoumarins↗
PubMed1977

The effect of a drug-resistance factor on recombination and repair of DNA in Escherichia coli K12.

The presence in recipient strains of Escherichia coli K12 of the plasmid R46 greatly reduced the yield of recombinants from crosses with several Hfr strains and virtually abolished the formation of recombinants by PI transduction without, however, significantly affecting the transfer of the F prime from a strain carrying Fgal. The R46 plasmid had paradoxical effects on mutability: it appeared to enhance the yield of mutants following irradiation with ultraviolet ligh but it reduced the number of mutants detectable in unirradiated cultures. The effects of this plasmid on ultraviolet survival of the wild type and several mutants defective for recombination and repair have been measured and the results, in the main, confirm similar observation by Tweats et al. (1976). Not only is the survival of the strain habouring R46 greater than that of the parent strain in all the cases studied, but the survival of ultraviolet irradiated bacteriophage lambda is also greater.

DNA Repair↗
PubMed2025

γ-tubulin mediates DNA double-strand break repair.

Double-strand breaks (DSBs) in DNA pose a critical threat to genomic integrity, potentially leading to the onset and progression of various diseases, including cancer. Cellular responses to such lesions entail sophisticated repair mechanisms primarily mediated by non-homologous end joining (NHEJ) and homologous recombination (HR). Interestingly, the efficient recruitment of repair proteins and completion of DSB repair likely involve complex, inter-organelle communication and coordination of cellular components. In this study, we report a role of γ-tubulin in DSB repair. γ-tubulin is a major microtubule nucleation factor governing microtubule dynamics. We show that γ-tubulin is recruited to the site of DNA damage and is required for efficient DSB repair via both NHEJ and HR. Suppression of γ-tubulin impedes DNA repair and exacerbates DNA damage accumulation. Furthermore, γ-tubulin mediates the mobilization and formation of DNA damage foci, which serve as repair centers, thereby facilitating the recruitment of HR and NHEJ repair proteins on damaged chromatin. Finally, pharmacological inhibition of γ-tubulin enhances the cytotoxic effect of DNA-damaging agents, consistent with the DNA repair function of γ-tubulin, and underscoring the potential of its therapeutic intervention in cancer therapy.

DNA Breaks, Double-Stranded↗
PubMed1978

Repair of cross-linked DNA and survival of Escherichia coli treated with psoralen and light: effects of mutations influencing genetic recombination and DNA metabolism.

Repair of cross-linked DNA was studied in Escherichia coli strains carrying mutations affecting DNA metabolism. In wild-type cells, DNA strands cut during cross-link removal were rejoined during a subsequent incubation into high-molecular-weight molecules. This rejoining was dependent on gene products involved in genetic recombination. A close correlation was found relating recombination proficiency, the rate of strand rejoining, and formation of viable progeny after DNA cross-linking by treatment with psoralen and light. Wild-type cells and other mutants which were Rec+ (sbcB, recL, recL sbcB, recB recC sbcA, recB recC sbcB, xthA1, and xthA11) rejoined cut DNA strands at a rate of 0.8 +/- 0.1 min -1 at 37 degrees C and survived 53 to 71 cross-links per chromosome. recB, recC, recB recC, recF, or polA strains showed reduced rates of strand rejoining and survived 4 to 13 cross-links per chromosome. Recombination-deficient strains (recA, recB recC sbcB recF, recB recL) and lexA failed to rejoin DNA strands after crosslink removal and were unable to form colonies after treatments producing as few as one to two cross-links per chromosome. Strand rejoining occurred normally in cells with mutations affecting DNA replication (dnaA, danB, dnaG, and dnaE) under both permissive and nonpermissive conditions for chromosome replication. In a polA polB dnaE strain strand rejoining occurred at 32 degree C but not at 42 degree C, indicating that some DNA synthesis was required for formation of intact recombinant molecules.

DNA Repair↗
PubMed2026

An IRAK1-snRNA axis activates ATM to promote accurate repair within transcriptionally active chromatin.

Genomic integrity in transcriptionally active regions is pivotal for suppressing oncogenic mutations, yet the mechanisms that govern precise homologous recombination (HR) repair within these regions remain elusive. Here, we report that the IRAK1-spliceosome axis operates with small nuclear RNA (snRNA) as a central hub, potently promoting accurate repair at DNA double-strand break (DSB) sites within active chromatin in human cancer cells. Mechanistically, IRAK1 phosphorylates spliceosomal serine/arginine (SR)-rich proteins to recruit snRNA to DSBs, inducing robust condensation of the MRE11-RAD50-NBS1 (MRN) complex near transcriptionally active regions to create an ATM activation platform. Collectively, our findings define a prevalent mechanism governing region-specific precise repair in transcriptionally active domains, where snRNA acts as a "transcription repair bridge" to link transcriptional processes to HR repair and ultimately preserves genomic stability. Inhibiting IRAK1 axis impairs HR repair in transcriptionally active regions, causing a marked increase in mutation rates specific to these regions and cancer-cell chemosensitivity.

Humans↗
PubMed2026

Dynamic chromatin tethering of MDC1 regulates genome stability.

DNA double-strand breaks (DSBs) are highly cytotoxic DNA lesions because they disrupt the connectivity of the DNA strand. Homologous recombination (HR) is a high-fidelity DSB repair pathway that copies the sequence spanning the break from a homologous template, but how DNA ends are held together during HR remains unclear. Here we demonstrate that the proline-serine-threonine (PST) repeat region of Mediator of DNA Damage Checkpoint 1 (MDC1) is a multivalent nucleosome-binding domain, sufficient to tether chromatin in multiple contexts. In interphase, the constitutive chromatin association of MDC1 is critical for RAD51 loading and efficient HR. In mitosis, PST-mediated chromatin binding is attenuated by phosphorylation, preventing aberrant chromosomal interactions while preserving DNA tethering by the MDC1-TOPBP1-CIP2A complex. In total, this work demonstrates that the PST repeat region of MDC1 is a multivalent nucleosome-binding domain with tunable affinity that supports DSB repair by HR and maintains genome stability during mitosis.

Genomic Instability↗
PubMed1976

Mutagen sensitivity of Drosophila melanogaster. III. X-linked loci governing sensitivity to methyl methanesulfonate.

Twenty-eight X-linked, recessive mutations of Drosophila melanogaster conferring enhanced sensitivity to the monofunctional alkylating agent, methyl methanesulfonate, have been recoered and assigned to five complementation groups. These groups can be distinguished on the basis of map location and variations in the pattern of mutagen sensitivity. Allelism of members of one complementation group with the previously described meiotic mutant, mei-41, (Baker and Carpenter, 1972) as well as the frequent appearance of female infertility with mutagen sensitivity suggests associated defects in meiotic chromosome behavior or early embryogenesis. Examination of the mutagen sensitivity of double mutants has led to the formulation of a working model of DNA repair for this organism. Studies of a similar nature (Boyd et al., 1976) have identified five additional X chromosome complementation groups, suggesting that the genome of Drosophila melanogaster may contain many loci involved with mutagen sensitivity. The continued isolation and characterization of conditional mutants of this type promises future insights into the mechanisms of DNA replication, DNA repair and recombination in this complex higher eucaryote.

Animals↗
PubMed2025

Moss BRCA2 lacking the canonical DNA-binding domain promotes homologous recombination and binds to DNA.

BRCA2 is crucial for mediating homology-directed DNA repair (HDR) through its binding to single-stranded DNA (ssDNA) and the recombinases RAD51 and DMC1. Most BRCA2 orthologs have a canonical DNA-binding domain (DBD) with the exception of Drosophila melanogaster. It remains unclear whether such a noncanonical BRCA2 variant without DBD possesses a DNA-binding activity. Here, we identify a new noncanonical BRCA2 in the model plant Physcomitrium patens (PpBRCA2). We establish that PpBRCA2 is essential for genome integrity maintenance, somatic DNA double-strand break (DSB) repair, HDR-mediated gene targeting, and RAD51 foci recruitment at DNA break sites. PpBRCA2 is also critical for DSB repair during meiosis. Interestingly, PpBRCA2 interacts strongly with RAD51 but weakly with DMC1, suggesting a distinct meiotic function compared to other BRCA2 homologs. Despite lacking the canonical DBD, PpBRCA2 binds ssDNA through its disordered N-terminal region and efficiently promotes HDR. Our work highlights that the ssDNA binding capacity of BRCA2 homologs is conserved regardless of the presence of a canonical DBD and provides a deeper understanding of BRCA2's functional diversity across species.

BRCA2 Protein↗
PubMed2025

Gene Editing and Protein Tagging in the Oomycete Phytophthora infestans Using CRISPR-Cas12a.

Molecular genetic tools such as CRISPR-Cas gene editing systems are invaluable for understanding gene and protein function and revealing the details of a pathogen's life and disease cycles. Here we present protocols for genome editing in Phytophthora infestans, an oomycete with global importance as a pathogen of potato and tomato. Using a vector system that expresses variants of Cas12a from Lachnospiraceae bacterium and its guide RNA from a unified transcript, we first present a method for editing genes through the non-homologous end-joining (NHEJ) pathway. We then describe an application of homology-directed repair (HDR), in which Cas12a is used to fuse a protein-coding gene with a fluorescent or epitope tag. Both methods should be adaptable to many oomycetes other than P. infestans.

Gene Editing↗
PubMed2026

Prime assembly with linear DNA donors enables large genomic insertions.

Targeted insertion of large DNA fragments has promising applications for genome engineering and gene therapy1,2. Twin prime-editing guide RNAs have enabled relatively large insertions, but the efficiency remains low for insertions greater than 400 base pairs3-6. Here we describe a prime assembly (PA) approach for the insertion of large DNA donor fragments, of which the ends are designed to overlap with the flaps generated by twin prime editing (twinPE). We used PA to insert one or multiple overlapping DNA fragments, with total insertion sizes ranging from 0.1 kb to 11 kb. An inhibitor of non-homologous end joining enhanced both the efficiency and precision of insertions. PA relies on DNA templates that are easily produced, does not require co-delivery of exogenous DNA-dependent DNA polymerases and proceeds in non-cycling cells, suggesting independence from canonical homology-directed repair pathways. Our study demonstrates that PA can initiate Gibson-like assembly in cells to generate gene insertions without double-stranded DNA breaks, recombinases or homology-directed repair.

Animals↗
PubMed1975

Isolation and characterization of mutants of Haemophilus influenzae deficient in an adenosine 5'-triphosphate-dependent deoxyribonuclease activity.

By a direct assay approach, mutants of Haemophilus influenzae Rd that are deficient in adenosine 5'-triphosphate-dependent deoxyribonuclease activity (add-) were isolated and characterized. A large proportion (50 to 90%) of the cells in cultures of these mutants failed to produce visible colonies when plated. An extensive analysis of the recombination proficiency of these strains revealed that the transformation frequency (transformants per competent cell) in the mutants was similar to that found in the wild type, but that the transformation efficiency (transformants per microgram of irreversibly bound deoxyribonucleic acid [DNA]) was reduced approximately fourfold. Sensitivities of the mutants to gamma rays, ultraviolet radiation, and methyl methane sulfonate were only slightly greater than wild-type levels. The rate of degradation of host DNA after ultraviolet irradiation was significantly reduced in the mutants. It is suggested that the adenosine 5'-triphosphate-dependent deoxyribonuclease in H. influenzae plays a nonessential role in DNA recombination and repair.

Adenosine Triphosphate↗
PubMed2025

Distinct roles of the two BRCA2 DNA-binding domains in DNA damage repair and replication fork preservation.

Homologous recombination (HR) removes DNA double-strand breaks (DSBs) and preserves stressed DNA replication forks. Successful HR execution requires the tumor suppressor BRCA2, which harbors distinct DNA-binding domains (DBDs): one that possesses three oligonucleotide/oligosaccharide-binding (OB) folds (OB-DBD) and another residing in the C-terminal recombinase binding domain (CTRB-DBD). Here, we employ multi-faceted approaches to delineate the contributions of these domains toward HR and replication fork maintenance. We show that OB-DBD and CTRB-DBD confer single-strand DNA (ssDNA)- and dsDNA-binding capabilities, respectively, and that BRCA2 variants mutated in either domain are impaired in their ability to load the recombinase RAD51 onto ssDNA pre-occupied by RPA. While the CTRB-DBD mutant is modestly affected by DNA break repair, it exhibits a strong defect in the protection of stressed replication forks. In contrast, the OB-DBD is indispensable for both BRCA2 functions. Our study thus defines the unique contributions of the two BRCA2 DBDs in genome maintenance.

BRCA2 Protein↗