BRCA1-associated structural variations are a consequence of polymerase theta-mediated end-joining

Kamp, Juliette A.; Schendel, Robin van; Dilweg, Ivar W.; Tijsterman, Marcel

doi:10.1038/s41467-020-17455-3

Cited by 46 publications

(83 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, DNA intermediates formed downstream of end resection and strand invasion may also be amenable to repair by TMEJ. This has recently been suggested to be the case when long-range resection is impaired due to mutations in BRCA1 , which may inhibit re-annealing of the unwound D-loop [ 22 ]. If so, mutations in genes involved in later steps of HR might also be synthetic lethal with POLQ mutations.…”

Section: Resultsmentioning

confidence: 99%

DNA polymerase theta suppresses mitotic crossing over

et al. 2021

View full text Add to dashboard Cite

Polymerase theta-mediated end joining (TMEJ) is a chromosome break repair pathway that is able to rescue the lethality associated with the loss of proteins involved in early steps in homologous recombination (e.g., BRCA1/2). This is due to the ability of polymerase theta (Pol θ) to use resected, 3’ single stranded DNA tails to repair chromosome breaks. These resected DNA tails are also the starting substrate for homologous recombination. However, it remains unknown if TMEJ can compensate for the loss of proteins involved in more downstream steps during homologous recombination. Here we show that the Holliday junction resolvases SLX4 and GEN1 are required for viability in the absence of Pol θ in Drosophila melanogaster, and lack of all three proteins results in high levels of apoptosis. Flies deficient in Pol θ and SLX4 are extremely sensitive to DNA damaging agents, and mammalian cells require either Pol θ or SLX4 to survive. Our results suggest that TMEJ and Holliday junction formation/resolution share a common DNA substrate, likely a homologous recombination intermediate, that when left unrepaired leads to cell death. One major consequence of Holliday junction resolution by SLX4 and GEN1 is cancer-causing loss of heterozygosity due to mitotic crossing over. We measured mitotic crossovers in flies after a Cas9-induced chromosome break, and observed that this mutagenic form of repair is increased in the absence of Pol θ. This demonstrates that TMEJ can function upstream of the Holiday junction resolvases to protect cells from loss of heterozygosity. Our work argues that Pol θ can thus compensate for the loss of the Holliday junction resolvases by using homologous recombination intermediates, suppressing mitotic crossing over and preserving the genomic stability of cells.

show abstract

Section: Resultsmentioning

confidence: 99%

DNA polymerase theta suppresses mitotic crossing over

et al. 2021

View full text Add to dashboard Cite

show abstract

“…In addition to inter-chromosomal translocations, BRCA1-deficient cells display <100 kb repeated sequences known as tandem duplications ( 53 , 145 ). Tandem duplications in BRCA1-deficient cells are often flanked by short regions of microhomology at the breakpoints, and are represented in mutational signature RS3 (Table 1 ) ( 78 ).…”

Section: Pol θ-Mediated Dsb Repair Promotes the Formation Of Tandem Dmentioning

confidence: 99%

“…In the simplest model, both sister chromatids are broken and erroneously fused together in a head-to-tail orientation by NHEJ or Pol θ-mediated end joining ( 145 , 146 ). Alternatively, tandem repeats may arise when end resection at two-ended DSBs is limited due to absence of BRCA1 ( 53 ). Resected ends with short 3′ ssDNA tails are a poor substrate for HR, but can be efficiently bound by Pol θ ( 58 , 147 ).…”

Section: Pol θ-Mediated Dsb Repair Promotes the Formation Of Tandem Dmentioning

confidence: 99%

“…Mutational signature ID8, characterized by small (<5 bp) deletions flanked by no to minor (>3 bp) microhomology at the break site, may be associated with DSB repair through NHEJ (Table 1 ) ( 4 , 17 ). ID8 is only mildly enriched in BRCA1/2-deficient tumours, indicating that NHEJ may only have a minor contribution to the repair of DSBs in the absence of HR ( 4 , 17 , 53 ).…”

Section: Erroneous Dsb Repair In Brca1/2-deficient Cells Introduces Imentioning

confidence: 99%

See 1 more Smart Citation

Shaping the BRCAness mutational landscape by alternative double-strand break repair, replication stress and mitotic aberrancies

Stok

Kok

Tempel

et al. 2021

Nucleic Acids Research

View full text Add to dashboard Cite

Tumours with mutations in the BRCA1/BRCA2 genes have impaired double-stranded DNA break repair, compromised replication fork protection and increased sensitivity to replication blocking agents, a phenotype collectively known as ‘BRCAness’. Tumours with a BRCAness phenotype become dependent on alternative repair pathways that are error-prone and introduce specific patterns of somatic mutations across the genome. The increasing availability of next-generation sequencing data of tumour samples has enabled identification of distinct mutational signatures associated with BRCAness. These signatures reveal that alternative repair pathways, including Polymerase θ-mediated alternative end-joining and RAD52-mediated single strand annealing are active in BRCA1/2-deficient tumours, pointing towards potential therapeutic targets in these tumours. Additionally, insight into the mutations and consequences of unrepaired DNA lesions may also aid in the identification of BRCA-like tumours lacking BRCA1/BRCA2 gene inactivation. This is clinically relevant, as these tumours respond favourably to treatment with DNA-damaging agents, including PARP inhibitors or cisplatin, which have been successfully used to treat patients with BRCA1/2-defective tumours. In this review, we aim to provide insight in the origins of the mutational landscape associated with BRCAness by exploring the molecular biology of alternative DNA repair pathways, which may represent actionable therapeutic targets in in these cells.

show abstract

“…Pol θ has helicase activity as well as microhomology-directed polymerase template switching and terminal transferase activities that insert extra nucleotides, sometimes untemplated, to leave characteristic “scars” between the tandemly joined sequences [ 23 , 109 , 110 ]. The role of Pol θ in forming TDs by error-prone alt-EJ has been confirmed by knockout studies in cancer tissue cultures [ 111 ] and supported by congruent results in the genetically tractable nematode worm, C. elegans [ 112 , 113 ].…”

Section: Published Results On Genome Structural Changes In Cancermentioning

confidence: 93%

How Chaotic Is Genome Chaos?

Shapiro

2021

Cancers

View full text Add to dashboard Cite

Cancer genomes evolve in a punctuated manner during tumor evolution. Abrupt genome restructuring at key steps in this evolution has been called “genome chaos.” To answer whether widespread genome change is truly chaotic, this review (i) summarizes the limited number of cell and molecular systems that execute genome restructuring, (ii) describes the characteristic signatures of DNA changes that result from activity of those systems, and (iii) examines two cases where genome restructuring is determined to a significant degree by cell type or viral infection. The conclusion is that many restructured cancer genomes display sufficiently unchaotic signatures to identify the cellular systems responsible for major oncogenic transitions, thereby identifying possible targets for therapies to inhibit tumor progression to greater aggressiveness.

show abstract

BRCA1-associated structural variations are a consequence of polymerase theta-mediated end-joining

Cited by 46 publications

References 64 publications

DNA polymerase theta suppresses mitotic crossing over

DNA polymerase theta suppresses mitotic crossing over

Shaping the BRCAness mutational landscape by alternative double-strand break repair, replication stress and mitotic aberrancies

How Chaotic Is Genome Chaos?

Contact Info

Product

Resources

About