Disparate pathways for extrachromosomal DNA biogenesis and genomic DNA repair
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE273081 | GEO | 2024/07/25
REPOSITORIES: GEO
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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:The DNA-dependent protein kinase (DNA-PK), which is composed of the KU heterodimer and the large catalytic subunit (DNA-PKcs), is a classical non-homologous end-joining (cNHEJ) factor. Naïve B cells undergo class switch recombination (CSR) to generate antibodies with different isotypes by joining two DNA double-strand breaks at different switching regions via the cNHEJ pathway. DNA-PK and the cNHEJ pathway play important roles in the DNA repair phase of CSR. To initiate cNHEJ, KU binds to DNA ends and recruits and activates DNA-PK. Activated DNA-PK phosphorylates DNA-PKcs at the S2056 and T2609 clusters. Loss of T2609 cluster phosphorylation increases radiation sensitivity but whether T2609 phosphorylation has a role in physiological DNA repair remains elusive. Using the DNA-PKcs5A mouse model carrying alanine substitutions at the T2609 cluster, here we show that loss of T2609 phosphorylation of DNA-PKcs does not affect the CSR efficiency. Yet, the CSR junctions recovered from DNA-PKcs5A/5A B cells reveal increased chromosomal translocations, extensive use of distal switch regions (consistent with end-resection), and preferential usage of micro-homology – all signs of the alternative end-joining pathway. Thus, these results uncover a role of DNA-PKcs T2609 phosphorylation in promoting cNHEJ repair pathway choice during CSR.
2020-07-18 | GSE154210 | GEO
Project description:DNA-PK is a heterotrimeric complex that consists of Ku70 (XRCC6), Ku80 (XRCC5) and DNA-PKcs (PRKDC) subunits. DNA-PK complex is a major player in DNA double strand break (DSB) repair via non-homologous end joining pathway. This process requires all of DNA-PK subunits. Ku70/Ku80 heterodimers firstly bind to DNA-ends at DSB, that increase affinity of DNA-PKcs to DNA-ends. Recruitment of DNA-PKcs subunit to DSB leads to phosphorylation events near DSB, recruitment of another NHEJ-related genes that restore DNA integrity. However, today a lot of evidence demonstrate participation of DNA-PK components in other cellular process, e.g. cytosolic DNA sensing, apoptosis regulation, cellular movement and adhesion. It is important to note that not all subunits of DNA-PK complex are necessary for these process. This demonstrate the independent functions of DNA-PK subunits. Here we for the first time using NGS-sequencing analyzed the transcriptional changes in HEK293T cells under depletion of Ku70, Ku80 or DNA-PKcs to characterize the independent functions of each subunit.
2021-07-23 | GSE180581 | GEO
Project description:In non-homologous end joining repair of DNA double strand breaks, DNA dependent protein kinase catalytic subunit (DNA-PKcs) and Ku70/80 binds the free DNA ends forming the holoenzyme DNA-PK. DNA-PK synapses across the break to tether the broken ends in the initial long range synaptic complex. We generated an integrative structural model of DNA-PK synapsis at a precision of 13.5Å with crosslinking mass spectrometry (XL-MS) restraints. While our hydrogen deuterium exchange (HX) analysis revealed an allosteric axis in DNA-PK connecting DNA binding (including the plug domain) to the kinase domain. Our model presents a symmetrical synapsis primarily through head to head interactions and protection of the DNA by previously uncharacterized a plug domain. The offset of the DNA in our model allows access to downstream processing enzymes, while the combination of DNA binding and kinase loading creates a tensed state that could have roles in the re-arrangement/dissociation of DNA-PKcs as the repair process progresses.
2021-01-20 | PXD017931 | Pride
Project description:The non-homologous end-joining (NHEJ) pathway is a major DNA double-strand break repair pathway in mammals and is essential for lymphocyte development. Ku70 and Ku80 heterodimer (KU) initiates NHEJ, thereby recruiting and activating the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs). While DNA-PKcs deletion only moderately impairs end-ligation, the expression of Kinase-dead DNA-PKcs completely abrogates NHEJ. Active DNA-PK phosphorylates DNA-PKcs at two clusters – PQR around S2056 (S2053 in mouse) and ABCDE around T2609. Alanine substitution at the S2056 cluster moderately compromises end-ligation on plasmid-based assays. But mice carrying alanine substitution at all 5 serine residues within the S2056 cluster (DNA-PKcsPQR/PQR) display no defect in lymphocyte development, leaving the physiological significance of S2056 cluster phosphorylation elusive. XLF is a non-essential NHEJ factor. Xlf-/- mice have substantial peripheral lymphocytes that are completely abolished by the loss of DNA-PKcs, the related ATM kinases, other chromatin associated DNA damage response factors (e.g., 53BP1, MDC1, H2AX, MRI, etc.) or RAG2-C-terminal regions, suggesting functional redundancy. While ATM inhibition does not further compromise end-ligation, here we show that in XLF-deficient background, DNA-PKcs S2056 cluster phosphorylation is critical for normal lymphocyte development. Chromosomal V(D)J recombination from DNA-PKcsPQR/PQRXlf-/- B cells is efficient but often has large deletions that jeopardize lymphocyte development. Class switch recombination junctions from DNA-PKcsPQR/PQRXlf-/- mice are less efficient and the residual junctions display decreased fidelity and increased deletion. These findings establish a role for DNA-PKcs S2056 cluster phosphorylation in physiological chromosomal NHEJ, implying that S2056 cluster phosphorylation contributes to the synergy between XLF and DNA-PKcs in end-ligation.
2023-05-01 | GSE228850 | GEO
Project description:The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is a classical nonhomologous end-joining (cNHEJ) factor. Loss of DNA-PKcs diminished mature B cell class switch recombination (CSR) to other isotypes, but not IgG1. Here, we show that expression of the kinase-dead DNA-PKcs (DNA-PKcsKD/KD) severely compromises CSR to IgG1. High-throughput sequencing analyses of CSR junctions reveal frequent accumulation of nonproductive interchromosomal translocations, inversions, and extensive end resection in DNA-PKcsKD/KD, but not DNA-PKcs-/- B cells. Meanwhile, the residual joints from DNA-PKcsKD/KDcells and the efficient Sμ-Sγ1 junctions from DNA-PKcs-/- B cells both display similar preferences for small (2–6 nt) microhomologies (MH). In DNA-PKcs-/- cells, Sμ-Sγ1 joints are more resistant to inversions and extensive resection than Sμ-Se and Sμ-Sμ joints, providing a mechanism for the isotype-specific CSR defects. Together, our findings identify a kinase-dependent role of DNA-PKcs in suppressing MH-mediated end joining and a structural role of DNA-PKcs protein in the orientation of CSR.
2018-07-26 | GSE117628 | GEO
Project description:The DNA-dependent protein kinase (DNA-PK), composed of the KU heterodimer and the catalytic subunit (DNA-PKcs), is a classical non-homologous end-joining (cNHEJ) factor1. KU binds to DNA ends, initiates cNHEJ, and recruits and activates DNA-PKcs. Beyond DNA, KU also binds to RNA, with unknown significance in mammals. Using mouse models, we uncovered an unexpected role for DNA-PK in ribosomal RNA (rRNA) biogenesis and hematopoiesis. Expression of kinase-dead (KD) DNA-PKcs (DNA-PKcsKD/KD) abroagates cNHEJ2. But DNA-PKcsKD/KDTp53-/- mice develop myeloid disease rather than pro-B cell lymphoma, like other cNHEJ/Tp53-deficient mice3. DNA-PKcs is its own the best substrate. Blocking DNA-PKcs phosphorylation at the T2609, but not the S2056 cluster leads to KU-dependent 18S rRNA processing defects, compromises global protein synthesis in hematopoietic cells and causes bone marrow failure in mice. KU drives assembly of DNA-PKcs on a broad array of cellular RNAs, including the U3 small nucleolar RNA (snoRNA), which is essential for 18S rRNA processing4. U3 activates purified DNA-PK and triggers T2609 phosphorylation. DNA-PK, but not other cNHEJ factors, resides in nucleoli in an rRNA-dependent manner and is co-purified with the small subunit (SSU) processome. Together our data show that DNA-PK has RNA-dependent, but cNHEJ-independent, functions during ribosome biogenesis that require DNA-PKcs’ kinase activity and T2609 cluster’s phosphorylation.
2020-01-05 | GSE109026 | GEO
Project description:DNA-PKcs is a crucial component of the non-homologous end joining (NHEJ) repair machinery. To investigate its function in human cell lines, we conducted a study using K562 and HEK293T cell lines. We introduced twinned DNA double-strand breaks (DSBs) or genome-wide DSBs into these cell lines via nucleofection and transfection, respectively. Subsequently, we employed high-throughput genome translocation sequencing (HTGTS) to capture the translocation events (i.e., ligation between "prey(s)" and "bait") and the rejoining events (i.e., direct repair within the "bait" locus) under different conditions, including with or without DNA-PKcs inhibition or deletion. We quantified the number of translocation events by normalizing them to the number of rejoining events, denoted as TL. Interestingly, DNA-PKcs inhibition led to an increase in TL, indicating a higher frequency of translocations. However, it is important to note that chromosomal translocations still predominantly relied on NHEJ despite DNA-PKcs inhibition. Furthermore, we observed that DNA-PKcs deletion resulted in an elevated utilization of microhomology in translocation formation. Nevertheless, NHEJ remained the primary mechanism driving translocation events.These findings provide valuable insights into the role of DNA-PKcs in the repair pathways involved in translocation events in human cell lines. The utilization of HTGTS allowed us to comprehensively analyze the effects of DNA-PKcs inhibition and deletion, shedding light on the interplay between NHEJ and alternative repair mechanisms in translocation formation.
2023-09-01 | GSE232940 | GEO
Project description:Circular extrachromosomal DNA (ecDNA) in patient tumor genomes is an important driver of oncogenic gene expression, evolution of drug resistance, and poor patient outcomes. Applying computational methods for detection and reconstruction of ecDNA across a retrospective cohort of 481 medulloblastoma (MB) tumors from 465 patients, we identify circular ecDNA in 82 patients (18%). Patients with ecDNA+ MB were more than twice as likely to relapse and three times as likely to die within 5 years of diagnosis. Individual tumors harbor multiple ecDNA lineages, each containing distinct amplified oncogenes. Multimodal sequencing, imaging, and CRISPR inhibition experiments in MB models reveal intratumoral heterogeneity of ecDNA copy number per cell and frequent putative "enhancer rewiring" events on ecDNA. This study reveals the frequency and diversity of ecDNA in a subset of highly aggressive MB tumors, and suggests copy number heterogeneity and enhancer rewiring as clinically relevant features of ecDNA in MB.
2023-09-15 | GSE240984 | GEO
Project description:Circular extrachromosomal DNA (ecDNA) in patient tumor genomes is an important driver of oncogenic gene expression, evolution of drug resistance, and poor patient outcomes. Applying computational methods for detection and reconstruction of ecDNA across a retrospective cohort of 481 medulloblastoma (MB) tumors from 465 patients, we identify circular ecDNA in 82 patients (18%). Patients with ecDNA+ MB were more than twice as likely to relapse and three times as likely to die within 5 years of diagnosis. Individual tumors harbor multiple ecDNA lineages, each containing distinct amplified oncogenes. Multimodal sequencing, imaging, and CRISPR inhibition experiments in MB models reveal intratumoral heterogeneity of ecDNA copy number per cell and frequent putative "enhancer rewiring" events on ecDNA. This study reveals the frequency and diversity of ecDNA in a subset of highly aggressive MB tumors, and suggests copy number heterogeneity and enhancer rewiring as clinically relevant features of ecDNA in MB.
2023-09-15 | GSE240830 | GEO