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Chromosomal translocations are guided by the spatial organization of the genome

ABSTRACT: The extent to which the three-dimensional organization of the genome contributes to chromosomal translocations is an important question in cancer genomics. We now have generated a high-resolution Hi-C spatial organization map of the G1-arrested mouse pro-B cell genome and mapped translocations from target DNA double-strand breaks (DSBs) within it via high-throughput genome-wide translocation sequencing. RAG endonuclease-cleaved antigen-receptor loci are dominant translocation partners for target DSBs regardless of genomic position, reflecting high frequency DSBs at these loci and their co-localization in a fraction of cells. To directly assess spatial proximity contributions, we normalized genomic DSBs via ionizing-radiation. Under these conditions, translocations were highly enriched in cis along single chromosomes containing target DSBs and within other chromosomes and sub-chromosomal domains in a manner directly related to pre-existing spatial proximity. Our studies reveal the power of combining two high-throughput genomic methods to address long-standing questions in cancer biology.

ORGANISM(S): Mus musculus

PROVIDER: GSE35519 | GEO | 2012/02/16

SECONDARY ACCESSION(S): PRJNA152237

REPOSITORIES: GEO

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Chromosomal translocations are guided by the spatial organization of the genome

Project description:The extent to which the three-dimensional organization of the genome contributes to chromosomal translocations is an important question in cancer genomics. We now have generated a high-resolution Hi-C spatial organization map of the G1-arrested mouse pro-B cell genome and mapped translocations from target DNA double-strand breaks (DSBs) within it via high-throughput genome-wide translocation sequencing. RAG endonuclease-cleaved antigen-receptor loci are dominant translocation partners for target DSBs regardless of genomic position, reflecting high frequency DSBs at these loci and their co-localization in a fraction of cells. To directly assess spatial proximity contributions, we normalized genomic DSBs via ionizing-radiation. Under these conditions, translocations were highly enriched in cis along single chromosomes containing target DSBs and within other chromosomes and sub-chromosomal domains in a manner directly related to pre-existing spatial proximity. Our studies reveal the power of combining two high-throughput genomic methods to address long-standing questions in cancer biology. Hi-C interaction maps for WT and ATM -/- G1-arrested AMuLV-transformed pro-B cell lines.

2012-02-16 | E-GEOD-35519 | biostudies-arrayexpress

Total protein abundances upon Mcm6 knockdown in the murine CH12 cells

Project description:Chromosomal translocations result from joining of DNA double-strand breaks (DSBs) and frequently cause cancer. Yet, the steps linking DSB formation to DSB ligation remain undeciphered. We report that DNA replication timing (RT) directly regulates lymphomagenic Myc translocations during antibody maturation in B-cells downstream of DSBs and independently of DSB frequency. Depletion of minichromosome-maintenance (MCM) complexes alters replication origin activity, decreases translocations and abrogates global RT. Ablating a single origin at Myc causes an early-to-late RT switch, loss of translocations and reduced nuclear proximity with a translocation partner locus, phenotypes that were reversed by restoring early RT. Disruption of shared early RT also reduced tumorigenic translocations in human leukemic cells. Thus, RT constitutes a new, unprecedented mechanism in translocation biogenesis linking DSB formation to DSB ligation

2022-09-13 | PXD034446 | Pride

DNA replication timing directly regulates the frequency of oncogenic chromosomal translocations

Project description:Chromosomal translocations result from the joining of DNA double-strand breaks (DSBs) and frequentlycause cancer. However, the steps linking DSB formation to DSB ligation remain undeciphered. Wereport that DNA replication timing (RT) directly regulates lymphomagenicMyctranslocations duringantibody maturation in B cells downstream of DSBs and independently of DSB frequency. Depletion ofminichromosome maintenance complexes alters replication origin activity, decreases translocations,and deregulates global RT. Ablating a single origin atMyccauses an early-to-late RT switch, loss oftranslocations, and reduced proximity with the immunoglobulin heavy chain (Igh) gene, its majortranslocation partner. These phenotypes were reversed by restoring early RT. Disruption of early RT alsoreduced tumorigenic translocations in human leukemic cells. Thus, RT constitutes a general mechanismin translocation biogenesis linking DSB formation to DSB ligation.

2022-09-15 | GSE161818 | GEO

Chromosome positioning and the clustering of functionally related loci in yeast is driven by chromosomal interactions

Project description:In recent years there has been considerable and growing interest in the 3-dimensional organization of genomes. In yeast this has included detailed FISH studies that show a surprising degree of spatial clustering of the tRNA genes, the localization of telomeres, centromere positioning, and global studies of chromosomal interactions.M-BM- In this study we performed an integrated biophysical M-bM-^@M-^S molecular study to produce the first high-resolution 3-dimensional reconstruction of a eukaryotic genome from first principles. Our conformations were produced using a using a molecular dynamics simulator to model the 16 yeast chromosomes as individual polymers. Critically, the compaction, folding and spatial organization of these chromosomes was informed by empirical data determined using proximity-based ligation. Our models allow us to investigate the structural organization and functional spatial clustering of the yeast nucleus at a resolution that has not previously been possible. We clearly show that yeast chromosomes have preferred yet non-exclusive positions. Surprisingly, while there are general trends relating chromosome position along the spindle pole body M-bM-^@M-^S nucleolus axis and chromosome size, some chromosomes have territories that contain two linked domains. Similarly, there is clear evidence for functional clustering of tRNAs and Gal4 protein binding sites. Intriguingly, these functional clusters are dynamic and the identity of the component elements alters in different model solutions. Genome Conformation Capture has been performed on exponentially growing Saccharomyces cerevisiae in media containing Glucose

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2017-04-19 | E-MTAB-4846 | biostudies-arrayexpress

Non-allelic homologous recombination between retrotransposable elements is a major driver of de novo unbalanced translocations.

Project description:Large scale analysis of balanced chromosomal translocation breakpoints has shown nonhomologous end joining and microhomology-mediated repair to be the main drivers of interchromosomal structural aberrations. Breakpoint sequences of de novo unbalanced translocations have not yet been investigated systematically. We analyzed 12 de novo translocations and mapped the breakpoints in 9. Surprisingly, in contrast to balanced translocations, we identify non-allelic homologous recombination (NAHR) between (retro)transposable elements and especially long interspersed elements (LINEs) as the main mutational mechanism. This finding implicates (retro)transposons to be a major driver of genomic rearrangements and exposes a profoundly different mutational mechanism compared to balanced chromosomal translocations. Furthermore, we show the existence of compound maternal/paternal derivative chromosomes, reinforcing the hypothesis that human cleavage stage embryogenesis is a cradle of chromosomal rearrangements. In total 36 non-amplified genomic DNA samples (12 patients plus parents) extracted from blood or amniocytes were analyzed by 250K Nsp I SNP arrays (GEO accession number GPL3718).

2012-07-12 | E-GEOD-39303 | biostudies-arrayexpress

Release of paused RNA-Polymerase II at specific introns and chromatin domains favors spontaneous DNA double strand break formation and predicts cancer translocations [RNA-seq]

Project description:Transcriptional activation leads to transient accumulation of DNA Double Strand Breaks (DSBs), which might promote formation of chromosomal translocations. We report here the genomic distribution of DSBs in non-transformed mammary cells grown under unperturbed conditions, using genome-wide Breaks Labeling In Situ and Sequencing (BLISS). We found thousands of high-confidence DSBs, which were enriched at the promoters of a subset of moderately- to highly-transcribed genes (fragile promoters) and co-localized with Topoisomerase II beta. Analyses of DSB-predictive features identified gene length and paused RNA Polymerase II, but not transcription, as critical factors (84% prediction accuracy). Analyses of DSB signaling and repair factors showed high levels of XRCC4, but not of gammaH2AX and NBS1, and no RAD51. Finally, the observed DSBs were predictive of a significant fraction of the recurrent translocations found in human breast cancers. These data suggest that, in normal cells, basal transcription from a specific class of promoters entails accumulation of TOP2B, leading to unresolved DSBs and increased probability of chromosomal translocations.

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Release of paused RNA-Polymerase II at specific introns and chromatin domains favors spontaneous DNA double strand break formation and predicts cancer translocations [ChIP-seq & BLISS]

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High-throughput sequencing of genome-wide translocations from stimulated wild-type or ATM-deficient B cells

Project description:High-throughput genome-wide translocation sequencing (HTGTS) is a robust approach to identify genome-wide translocation junctions. We performed HTGTS to study the fate of introduced c-myc DSBs in mouse splenic B cells activated for activation cytidine deaminase (AID)-dependent class switch recombination (CSR). We found frequent translocations of c-myc DSBs to AID-initiated DSBs in IgH switch regions in wild-type (WT) and ATM-deficient B cells. However, c-myc also translocated frequently to newly generated DSBs within a 35-megabase region downstream of IgH in ATM-deficient, but not WT, CSR-activated B cells. Moreover, we found such DSBs and translocations in activated B cells that did not express AID or undergo CSR. These findings indicate that ATM deficiency leads to formation of chromosome 12 dicentrics via RAG-initiated IgH DSBs in progenitor B cells and that these dicentrics can be propagated developmentally into mature B cells where they generate new DSBs downstream of IgH via breakage-fusion-bridge cycles. Preparation of libraries from WT or ATM-deficient activated by a-CD40/IL4 or RP105.

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Non-allelic homologous recombination between retrotransposable elements is a major driver of de novo unbalanced translocations.

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