Genome-wide Translocation Sequencing Reveals Mechanisms of Chromosome Breaks and Rearrangements in B Cells
Ces deux études dressent, à l'échelle du génome, une cartographie des translocations chromosomiques dans les lymphocytes T et identifient des loci présentant une susceptibilité spécifique pour des réarrangements chromosomiques
Whereas chromosomal translocations are common pathogenetic events in cancer, mechanisms that promote them are poorly understood. To elucidate translocation mechanisms in mammalian cells, we developed high-throughput, genome-wide translocation sequencing (HTGTS). We employed HTGTS to identify tens of thousands of independent translocation junctions involving fixed I-SceI meganuclease-generated DNA double-strand breaks (DSBs) within the c-myc oncogene or IgH locus of B lymphocytes induced for activation-induced cytidine deaminase (AID)-dependent IgH class switching. DSBs translocated widely across the genome but were preferentially targeted to transcribed chromosomal regions. Additionally, numerous AID-dependent and AID-independent hot spots were targeted, with the latter comprising mainly cryptic I-SceI targets. Comparison of translocation junctions with genome-wide nuclear run-ons revealed a marked association between transcription start sites and translocation targeting. The majority of translocation junctions were formed via end-joining with short microhomologies. Our findings have implications for diverse fields, including gene therapy and cancer genomics. º A new genome-wide sequencing technique identifies translocations º DSBs translocate preferentially to transcription start sites º End-joining with microhomologies joins DSB-induced translocations º Translocation hot spots in primary B cells targeted by AID activity A new method detects thousands of chromosomal translocations, showing that they home to transcriptional start sites, AID-dependent hot spots, and gene-rich regions.
Cell , résumé, 2010