Expansions and Contractions in a Tandem Repeat Induced by Double-Strand Break Repair

ABSTRACT Repair of a double-strand break (DSB) in yeast can induce very frequent expansions and contractions in a tandem array of 375-bp repeats. These results strongly suggest that DSB repair can be a major source of amplification of tandemly repeated sequences. Most of the DSB repair events are not associated with crossover. Rearrangements appear in 50% of these repaired recipient molecules. In contrast, the donor template nearly always remains unchanged. Among the rare crossover events, similar rearrangements are found. These results cannot readily be explained by the gap repair model of Szostak et al. (J. W. Szostak, T. L. Orr-Weaver, R. J. Rothstein, and F. W. Stahl, Cell 33:25–35, 1983) but can be explained by synthesis-dependent strand annealing (SDSA) models that allow for crossover. Support for SDSA models is provided by a demonstration that a single DSB repair event can use two donor templates located on two different chromosomes.

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Watching a double strand break repair polymerase insert a pro-mutagenic oxidized nucleotide

Nature Communications ◽

10.1038/s41467-021-21354-6 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Joonas A. Jamsen ◽

Akira Sassa ◽

David D. Shock ◽

William A. Beard ◽

Samuel H. Wilson

Keyword(s):

Active Site ◽

Dna Polymerases ◽

Time Lapse ◽

Strand Break ◽

Double Strand Break ◽

Double Strand Break Repair ◽

Dsb Repair ◽

X Ray Crystallography ◽

Polymerase Fidelity ◽

Break Repair

AbstractOxidized dGTP (8-oxo-7,8-dihydro-2´-deoxyguanosine triphosphate, 8-oxodGTP) insertion by DNA polymerases strongly promotes cancer and human disease. How DNA polymerases discriminate against oxidized and undamaged nucleotides, especially in error-prone double strand break (DSB) repair, is poorly understood. High-resolution time-lapse X-ray crystallography snapshots of DSB repair polymerase μ undergoing DNA synthesis reveal that a third active site metal promotes insertion of oxidized and undamaged dGTP in the canonical anti-conformation opposite template cytosine. The product metal bridged O8 with product oxygens, and was not observed in the syn-conformation opposite template adenine (At). Rotation of At into the syn-conformation enabled undamaged dGTP misinsertion. Exploiting metal and substrate dynamics in a rigid active site allows 8-oxodGTP to circumvent polymerase fidelity safeguards to promote pro-mutagenic double strand break repair.

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mus309 mutation, defective in DNA double-strand break repair, affects intergenic but not intragenic meiotic recombination in Drosophila melanogaster

Genetics Research ◽

10.1017/s0016672305007883 ◽

2005 ◽

Vol 86 (3) ◽

pp. 185-191 ◽

Cited By ~ 10

Author(s):

PETTER PORTIN

Keyword(s):

X Chromosome ◽

Meiotic Recombination ◽

Strand Break ◽

Double Strand Break ◽

Double Strand Break Repair ◽

Crossing Over ◽

Dna Double Strand Break ◽

D Loop ◽

Break Repair ◽

Strand Annealing

The effect was investigated of the hypomorphic DNA double-strand break repair, notably synthesis-dependent strand annealing, deficient mutation mus309 on the third chromosome of Drosophila melanogaster on intergenic and intragenic meiotic recombination in the X chromosome. The results showed that the mutation significantly increases the frequency of intergenic crossing over in two of three gene intervals of the X chromosome studied. Interestingly the increase was most prevalent in the tip of the X chromosome where crossovers normally are least frequent per physical map unit length. In particular crossing over interference was also affected, indicating that the effect of the mus309 mutation involves preconditions of crossing over but not the event of crossing over itself. On the other hand, the results also show that most probably the mutation does not have any effect on intragenic recombination, i.e. gene conversion. These results are fully consistent with the present molecular models of meiotic crossing over initiated by double-strand breaks of DNA followed by formation of a single-end-invasion intermediate, or D-loop, which is subsequently processed to generate either crossover or non-crossover products involving formation of a double Holliday junction. In particular the results suggest that the mus309 gene is involved in resolution of the D-loop, thereby affecting the choice between double-strand-break repair (DSBR) and synthesis-dependent strand annealing (SDSA) pathways of meiotic recombination.

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Second-Generation Antiandrogen Therapy Radiosensitizes Prostate Cancer Regardless of Castration State through Inhibition of DNA Double Strand Break Repair

Cancers ◽

10.3390/cancers12092467 ◽

2020 ◽

Vol 12 (9) ◽

pp. 2467 ◽

Cited By ~ 1

Author(s):

Mohamed E. Elsesy ◽

Su Jung Oh-Hohenhorst ◽

Anastassia Löser ◽

Christoph Oing ◽

Sally Mutiara ◽

...

Keyword(s):

Prostate Cancer ◽

First Generation ◽

Second Generation ◽

Strand Break ◽

Double Strand Break ◽

Abiraterone Acetate ◽

Double Strand Break Repair ◽

Dsb Repair ◽

Castration Resistant ◽

Break Repair

(1) Background: The combination of the first-generation antiandrogens and radiotherapy (RT) has been studied extensively in the clinical setting of prostate cancer (PCa). Here, we evaluated the potential radiosensitizing effect of the second-generation antiandrogens abiraterone acetate, apalutamide and enzalutamide. (2) Methods: Cell proliferation and agarose-colony forming assay were used to measure the effect on survival. Double strand break repair efficiency was monitored using immunofluorescence staining of γH2AX/53BP1. (3) Results: We report retrospectively a minor benefit for PCa patients received first-generation androgen blockers and RT compared to patients treated with RT alone. Combining either of the second-generation antiandrogens and 2Gy suppressed cell growth and increased doubling time significantly more than 2Gy alone, in both hormone-responsive LNCaP and castration-resistant C4-2B cells. These findings were recapitulated in resistant sub-clones to (i) hormone ablation (LNCaP-abl), (ii) abiraterone acetate (LNCaP-abi), (iii) apalutamide (LNCaP-ARN509), (iv) enzalutamide (C4-2B-ENZA), and in castration-resistant 22-RV1 cells. This radiosensitization effect was not observable using the first-generation antiandrogen bicalutamide. Inhibition of DNA DSB repair was found to contribute to the radiosensitization effect of second-generation antiandrogens, as demonstrated by a significant increase in residual γH2AX and 53BP1 foci numbers at 24h post-IR. DSB repair inhibition was further demonstrated in 22 patient-derived tumor slice cultures treated with abiraterone acetate before ex-vivo irradiation with 2Gy. (4) Conclusion: Together, these data show that second-generation antiandrogens can enhance radiosensitivity in PCa through DSB repair inhibition, regardless of their hormonal status. Translated into clinical practice, our results may help to find additional strategies to improve the effectiveness of RT in localized PCa, paving the way for a clinical trial.

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The deinococcal DdrB protein is involved in an early step of DNA double strand break repair and in plasmid transformation through its single-strand annealing activity

DNA Repair ◽

10.1016/j.dnarep.2011.09.010 ◽

2011 ◽

Vol 10 (12) ◽

pp. 1223-1231 ◽

Cited By ~ 32

Author(s):

Claire Bouthier de la Tour ◽

Stéphanie Boisnard ◽

Cédric Norais ◽

Magali Toueille ◽

Esma Bentchikou ◽

...

Keyword(s):

Strand Break ◽

Double Strand Break ◽

Single Strand ◽

Double Strand Break Repair ◽

Early Step ◽

Plasmid Transformation ◽

Dna Double Strand Break ◽

Single Strand Annealing ◽

Break Repair ◽

Strand Annealing

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Involvement of POLA2 in Double Strand Break Repair and Genotoxic Stress

International Journal of Molecular Sciences ◽

10.3390/ijms21124245 ◽

2020 ◽

Vol 21 (12) ◽

pp. 4245

Author(s):

Tuyen T. Dang ◽

Julio C. Morales

Keyword(s):

Dna Damage ◽

Genomic Instability ◽

Dna Polymerase ◽

Genotoxic Stress ◽

Strand Break ◽

Double Strand Break ◽

Double Strand Break Repair ◽

Dsb Repair ◽

Dna Polymerase Alpha ◽

Break Repair

Cellular survival is dependent on the efficient replication and transmission of genomic information. DNA damage can be introduced into the genome by several different methods, one being the act of DNA replication. Replication is a potent source of DNA damage and genomic instability, especially through the formation of DNA double strand breaks (DSBs). DNA polymerase alpha is responsible for replication initiation. One subunit of the DNA polymerase alpha replication machinery is POLA2. Given the connection between replication and genomic instability, we decided to examine the role of POLA2 in DSB repair, as little is known about this topic. We found that loss of POLA2 leads to an increase in spontaneous DSB formation. Loss of POLA2 also slows DSB repair kinetics after treatment with etoposide and inhibits both of the major double strand break repair pathways: non-homologous end-joining and homologous recombination. In addition, loss of POLA2 leads to increased sensitivity to ionizing radiation and PARP1 inhibition. Lastly, POLA2 expression is elevated in glioblastoma multiforme tumors and correlates with poor overall patient survival. These data demonstrate a role for POLA2 in DSB repair and resistance to genotoxic stress.

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