Ontology highlight
ABSTRACT:
PROVIDER: PRJNA953777 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR24112630_subreads.fastq.gz | Fastqsanger.gz | |||
| SRR24112631_subreads.fastq.gz | Fastqsanger.gz | |||
| SRR24112632_subreads.fastq.gz | Fastqsanger.gz | |||
| SRR24112633_subreads.fastq.gz | Fastqsanger.gz | |||
| SRR24112634_subreads.fastq.gz | Fastqsanger.gz |
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Project description:To generate antibodies with different effector functions, B cells undergo Immunoglobulin class switch recombination (CSR). The ligation step of CSR is usually mediated by the classical non-homologous end-joining (cNHEJ) pathway. In cNHEJ-deficient cells, a remarkable ~25% CSR can be achieved by the alternative end-joining (A-EJ) pathway that preferentially uses microhomology (MH) at the junctions. While A-EJ mediated repair of endonuclease generated breaks requires DNA end-resection, we show that CtIP-mediated DNA end-resection is dispensable for A-EJ-mediated CSR using cNHEJ-deficient B cells. High-throughput sequencing analyses revealed that loss of ATM/ATR phosphorylation of CtIP at T855 or ATM kinase inhibition suppress resection without altering the MH-pattern of the A-EJ-mediated switch junctions. Moreover, we found that ATM kinase promotes Alt-EJ mediated CSR by suppressing inter-chromosomal translocations independent of end-resection. Finally, temperol analyses reveal that MHs are enriched in early internal deletions even in cNHEJ-proficient B cells. Thus, we propose that repetitive IgH switch regions represent favoriate substrates for MH-mediated end-joining contributing to the robustness and resection-indepndence of A-EJ-mediated CSR.
2020-09-18 | GSE156392 | GEO
Project description:The CRISPR system is widely used in genome editing for biomedical research. Here, using either dual paired Cas9D10A nickases or paired Cas9 nuclease we characterise unintended larger deletions at on-target sites that frequently evade common genotyping practices. We found that unintended larger deletions are prevalent at multiple distinct loci on different chromosomes, in cultured cells and mouse embryos alike. We observed a high frequency of microhomologies at larger deletion breakpoint junctions, suggesting the involvement of microhomology-mediated end joining in their generation. In populations of edited cells, the distribution of larger deletion sizes is dependent on proximity to sgRNAs and cannot be predicted by microhomology sequences alone.
2019-05-13 | GSE130621 | GEO
Project description:Two DNA repair pathways, non-homologous end joining (NHEJ) and alternative end joining (A-EJ), are involved in V(D)J recombination and chromosome translocation. Previous studies reported distinct repair mechanisms for chromosome translocation, with NHEJ predominantly involved in human and A-EJ in mice. NHEJ depends on DNA-PKcs, a critical partner in synapsis formation and downstream component activation. While DNA-PKcs inhibition promotes chromosome translocations harboring microhomologies in mice, its synonymous effect in human is not known. We find partial DNA-PKcs inhibition in human cell lines leads to increased genome-wide translocations composed mostly of direct joints, indicating the continued involvement of dampened NHEJ in these processes. In contrast, complete DNA-PKcs inhibition and genetic inhibition DNA-PKcs kinase domain substantially increased microhomology-mediated end joining (MMEJ), thus bridging the two different translocation mechanisms between human and mice. Similar to a previous study on Ku70 deletion, DNA-PKcs deletion in G1/G0-phase mouse pro-B cell lines, impair the recombination of RAG1/2-mediated DNA double-strand breaks (DSBs). This DNA-PKcs-deficient repair mechanism exhibited reduced V(D)J recombination efficiency, increased end resection, decreased polymerase-mediated insertions, loss of recombination fidelity and generated relatively higher rates of chromosome translocation as a consequence of dysregulated coding and signal end joining. Our study underscores DNA-PKcs in suppressing illegitimate chromosome rearrangement in both species.
2023-12-30 | GSE249453 | GEO
Project description:Determining the balance between DNA double strand break repair (DSBR) pathways is essential for understanding treatment response in cancer. We report a novel method for simultaneously measuring non-homologous end joining (NHEJ), homologous recombination (HR), and microhomology-mediated end joining (MMEJ). This approach revealed enhanced MMEJ and HR in glioblastoma (GBM) xenograft models with acquired temozolomide (TMZ) resistance. Knockdown of proteins in either pathway enhanced killing by TMZ, and a targeted screen identified pharmacological-grade dual HR/MMEJ inhibitors, including AZD1390, an ATM kinase inhibitor. AZD1390 suppressed DSB end resection, blocked phosphorylation of end protection proteins in response to DNA damage, and potentiated TMZ in treatment-naïve and treatment-resistant models. TP53-mutant GBMs were most susceptible to AZD1390 in combination with DNA-damaging agents due to elevated ATM-dependent HR/MMEJ, preferential activation of these pathways in response to DNA damage, and a defective G2/M checkpoint, which caused these GBMs to enter mitosis despite unrepaired DNA damage, leading to cell death via apoptosis. This report establishes ATM-dependent HR and MMEJ as targetable resistance mechanisms in TP53-mutant GBM and establishes an approach for simultaneously measuring multiple DSBR pathways in treatment selection and oncology research.
2024-03-08 | PXD047837 | Pride
Project description:Ubiquitination is a crucial post-translational modification required for the proper repair of DNA double-strand breaks (DSBs) induced by ionising radiation (IR). DSBs are mainly repaired through homologous recombination (HR) when template DNA is present and non-homologous end joining (NHEJ) in its absence. Additionally, microhomology-mediated end joining (MMEJ) and single strand annealing (SSA) provide back-up DSBs repair pathways. However, the mechanisms controlling their use remain poorly understood. By employing a high-resolution CRISPR screen of the ubiquitin system after IR, we systematically uncover genes required for cell survival and elucidate a critical role of the E3 ubiquitin ligase SCFcyclin F in cell cycle dependent DSB repair. We show that SCFcyclin F -mediated EXO1 degradation prevents DNA end resection in mitosis, allowing MMEJ to take place. Moreover, we identify a conserved cyclin F recognition motif, distinct from the one used by other cyclins, with broad implications in cyclin specificity for cell cycle control.
2024-10-17 | PXD051841 | Pride
Project description:Oncogene amplification on extrachromosomal DNA (ecDNA) is a pervasive driver event in cancer, yet our understanding of how ecDNA forms is limited. Here, we couple a CRISPR-based method for ecDNA induction with extensive characterization of newly formed ecDNA to examine their biogenesis. We find that DNA circularization is efficient, irrespective of 3D genome context, with formation of 800kb, 1 Mb, and 1.8 Mb ecDNAs reaching or exceeding 15%. We show non-homologous end joining and microhomology-mediated end joining both contribute to ecDNA formation, while inhibition of DNA-PKcs and ATM have opposing impacts on ecDNA formation. EcDNA and the corresponding chromosomal excision scar can form at significantly different rates and respond differently to DNA-PKcs and ATM inhibition. Taken together, our results support a model of ecDNA formation in which double strand break ends dissociate from their legitimate ligation partners prior to joining of illegitimate ends to form the ecDNA and excision scar.
2024-07-25 | GSE273081 | GEO
Project description:DNA double strand breaks (DSBs) are a major source of mutations. Both non-homologous-end-joining (NHEJ) and microhomology-mediated-end-joining (MMEJ) DSB repair pathways are error prone and produce deletions, which can lead to cancer. DSBs also lead to epigenetic changes, including demethylation, which is involved in carcinogenesis. Of specific interest is the MMEJ repair pathway, as it requires methylation restoration around the break, as a result of the resection and formation of single stranded (ssDNA) intermediates. While, methylation patterns after homologous recombination (HR) have been partially studied, the methylation status after MMEJ and NHEJ remains poorly reported, and can be relevant for cancer. To study methylation patterns around DSB after NHEJ and MMEJ repair, we used targeted bisulfite-sequencing (BS-seq) to quantify methylation of dozens of single cell clones after induction of DSB by CRISPR. Each single cell clone was classified according to the sequence signature to a specific repair mechanism: NHEJ or MMEJ. Comparison of single cell clones after DSB to control cells, without DSB, demonstrated correct restoration of the methylation levels. No difference in methylation patterns was noticed when comparing NHEJ to MMEJ. Methylation levels in gene body, highly methylated CpGs (n=61, 4000 base pairs around DSB) and in low methylation CpGs (n=19), remained stable after both MMEJ and NHEJ. Gene body methylation persisted even on the background of DNMT3A R882C mutation, the most prevalent preleukemic mutation, in which the de novo methylation machinery is compromised. An exception observed in a single CpG site (ASXL1 995) which demonstrated elevated methylation rate after DSB repair only in the presence of WT DNMT3A. In summary, DNA methylation restoration demonstrated high fidelity after DSB both in methylated and unmethylated gene body, even in cases where DNA resections and deletions occurred.
2022-09-11 | E-MTAB-12037 | biostudies-arrayexpress