Helicase Q promotes homology-driven DNA double-strand break repair and prevents tandem duplications

Kamp, Juliette A.; Lemmens, Bennie B. L. G.; Romeijn, Ron J.; Changoer, S. C.; Schendel, Robin van; Tijsterman, Marcel

doi:10.1038/s41467-021-27408-z

Cited by 20 publications

(23 citation statements)

References 72 publications

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“…It is believed that the synthesis-dependent strand annealing (SDSA) is the most relevant subpathway in the repair of IR-induced DSBs by HR. In this final step, the newly synthesized strand anneals with the similarly processed second DNA strand to restore integrity in the molecule, and the process is completed by DNA synthesis and ligation [ 84 , 85 ].…”

Section: Dsb Repair Pathwaysmentioning

confidence: 99%

DNA Damage Clustering after Ionizing Radiation and Consequences in the Processing of Chromatin Breaks

et al. 2022

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Charged-particle radiotherapy (CPRT) utilizing low and high linear energy transfer (low-/high-LET) ionizing radiation (IR) is a promising cancer treatment modality having unique physical energy deposition properties. CPRT enables focused delivery of a desired dose to the tumor, thus achieving a better tumor control and reduced normal tissue toxicity. It increases the overall radiation tolerance and the chances of survival for the patient. Further improvements in CPRT are expected from a better understanding of the mechanisms governing the biological effects of IR and their dependence on LET. There is increasing evidence that high-LET IR induces more complex and even clustered DNA double-strand breaks (DSBs) that are extremely consequential to cellular homeostasis, and which represent a considerable threat to genomic integrity. However, from the perspective of cancer management, the same DSB characteristics underpin the expected therapeutic benefit and are central to the rationale guiding current efforts for increased implementation of heavy ions (HI) in radiotherapy. Here, we review the specific cellular DNA damage responses (DDR) elicited by high-LET IR and compare them to those of low-LET IR. We emphasize differences in the forms of DSBs induced and their impact on DDR. Moreover, we analyze how the distinct initial forms of DSBs modulate the interplay between DSB repair pathways through the activation of DNA end resection. We postulate that at complex DSBs and DSB clusters, increased DNA end resection orchestrates an increased engagement of resection-dependent repair pathways. Furthermore, we summarize evidence that after exposure to high-LET IR, error-prone processes outcompete high fidelity homologous recombination (HR) through mechanisms that remain to be elucidated. Finally, we review the high-LET dependence of specific DDR-related post-translational modifications and the induction of apoptosis in cancer cells. We believe that in-depth characterization of the biological effects that are specific to high-LET IR will help to establish predictive and prognostic signatures for use in future individualized therapeutic strategies, and will enhance the prospects for the development of effective countermeasures for improved radiation protection during space travel.

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Section: Dsb Repair Pathwaysmentioning

confidence: 99%

DNA Damage Clustering after Ionizing Radiation and Consequences in the Processing of Chromatin Breaks

et al. 2022

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“…Alternatively, HELQ might be crucial for the strand annealing stage of SDSA after the D-loop is unwound. Two recent studies identified a role for C. elegans and mammalian HELQ in annealing complementary ssDNA strands during microhomology-mediated end-joining and homologous recombination [ 43 , 44 ]. Drosophila HELQ has also been implicated in single-strand annealing repair [ 45 ].…”

Section: Discussionmentioning

confidence: 99%

Division of Labor by the HELQ, BLM, and FANCM Helicases during Homologous Recombination Repair in Drosophila melanogaster

Childress

Cox

Wolfe

et al. 2022

Genes

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Repair of DNA double-strand breaks by homologous recombination (HR) requires a carefully orchestrated sequence of events involving many proteins. One type of HR, synthesis-dependent strand annealing (SDSA), proceeds via the formation of a displacement loop (D-loop) when RAD51-coated single-stranded DNA invades a homologous template. The 3′ end of the single-stranded DNA is extended by DNA synthesis. In SDSA, the D-loop is then disassembled prior to strand annealing. While many helicases can unwind D-loops in vitro, how their action is choreographed in vivo remains to be determined. To clarify the roles of various DNA helicases during SDSA, we used a double-strand gap repair assay to study the outcomes of homologous recombination repair in Drosophila melanogaster lacking the BLM, HELQ, and FANCM helicases. We found that the absence of any of these three helicases impairs gap repair. In addition, flies lacking both BLM and HELQ or HELQ and FANCM had more severe SDSA defects than the corresponding single mutants. In the absence of BLM, a large percentage of repair events were accompanied by flanking deletions. Strikingly, these deletions were mostly abolished in the blm helq and blm fancm double mutants. Our results suggest that the BLM, HELQ, and FANCM helicases play distinct roles during SDSA, with HELQ and FANCM acting early to promote the formation of recombination intermediates that are then processed by BLM to prevent repair by deletion-prone mechanisms.

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“…These observations are consistent with supplementary CNHEJ-mediated repair compensating for the insufficiency of POLQ-dependent ANHEJ ( 12 ). An alternative prospect is that, in the absence of POLQ, substituted repair processes ( 110 ) exploit MH more distant from the ultimate fusion junction to stabilize the ligation and these may have been omitted from our analyses. In contrast, we determined enhanced MH usage at the inter-chromosomal telomere fusions that are also more abundant in POLQ –/– clones.…”

Section: Discussionmentioning

confidence: 99%

“…While appearing incongruous with the supposition that CNHEJ is the prevailing mode of repair at these junctions ( 111 , 112 ), the actual lengths of MH employed at inter-chromosomal fusion junctions were lesser than those at genomic and intra-chromosomal fusion junctions and were further tempered by POLQ deficiency. The discrepancies in MH lengths at POLQ-independent inter-chromosomal compared with genomic and intra-chromosomal fusions (means of 2.37, 4.14 and 6.44 bp, respectively) suggest distinct processing and end-ligation mechanisms propel inter-chromosomal rearrangements, while refuting the likelihood of diversion into repair processes dependent on more extensive MH, such as single-strand annealing ( 107 , 110 , 113 , 114 ).…”

Section: Discussionmentioning

confidence: 99%

“…ANHEJ debilitated by POLQ disruption is surpassed by the efficiency and competency of CNHEJ that ligates distant DSB to conserve chromosome integrity. Thus, increases in long-range telomere–satellite recombinations in the absence of POLQ are products of the shift in DNAR capacity ( 110 ) coupled with variability at repeat tracts that amplifies the vulnerability of these loci.…”

Section: Discussionmentioning

confidence: 99%

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POLQ suppresses genome instability and alterations in DNA repeat tract lengths

et al. 2022

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DNA polymerase theta (POLQ) is a principal component of the alternative non-homologous end-joining (ANHEJ) DNA repair pathway that ligates DNA double-strand breaks. Utilizing independent models of POLQ insufficiency during telomere-driven crisis, we found that POLQ–/– cells are resistant to crisis-induced growth deceleration despite sustaining inter-chromosomal telomere fusion frequencies equivalent to wild-type (WT) cells. We recorded longer telomeres in POLQ–/– than WT cells pre- and post-crisis, notwithstanding elevated total telomere erosion and fusion rates. POLQ–/– cells emerging from crisis exhibited reduced incidence of clonal gross chromosomal abnormalities in accordance with increased genetic heterogeneity. High-throughput sequencing of telomere fusion amplicons from POLQ-deficient cells revealed significantly raised frequencies of inter-chromosomal fusions with correspondingly depreciated intra-chromosomal recombinations. Long-range interactions culminating in telomere fusions with centromere alpha-satellite repeats, as well as expansions in HSAT2 and HSAT3 satellite and contractions in ribosomal DNA repeats, were detected in POLQ–/– cells. In conjunction with the expanded telomere lengths of POLQ–/– cells, these results indicate a hitherto unrealized capacity of POLQ for regulation of repeat arrays within the genome. Our findings uncover novel considerations for the efficacy of POLQ inhibitors in clinical cancer interventions, where potential genome destabilizing consequences could drive clonal evolution and resistant disease.

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Helicase Q promotes homology-driven DNA double-strand break repair and prevents tandem duplications

Cited by 20 publications

References 72 publications

DNA Damage Clustering after Ionizing Radiation and Consequences in the Processing of Chromatin Breaks

DNA Damage Clustering after Ionizing Radiation and Consequences in the Processing of Chromatin Breaks

Division of Labor by the HELQ, BLM, and FANCM Helicases during Homologous Recombination Repair in Drosophila melanogaster

POLQ suppresses genome instability and alterations in DNA repeat tract lengths

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