Nbs1 ChIP-Seq Identifies Off-Target DNA Double-Strand Breaks Induced by AID in Activated Splenic B Cells

摘要: Activation-induced cytidine deaminase (AID) is required for initiation of Ig class switch recombination (CSR) and somatic hypermutation (SHM) antibody genes during immune responses. AID has also been shown to induce chromosomal translocations, mutations, DNA double-strand breaks (DSBs) involving non-Ig in activated B cells. To determine what makes a site target AID-induced DSBs, we identify off-target DSBs induced by performing chromatin immunoprecipitation (ChIP) Nbs1, protein that binds followed deep sequencing (ChIP-Seq). We detect characterize hundreds AID-dependent DSBs. Two types tandem repeats are highly enriched within the Nbs1-binding sites: long CA repeats, which can form Z-DNA, pentamers containing hotspot WGCW. These not nearly as at AID-independent identified. Msh2, component mismatch repair pathway important genome stability, increases similar its effect on region intermediates CSR. Most two-ended, consistent with generation G1 phase, regions. However, minority one-ended, presumably due conversion single-strand replication. One-ended repaired processes homologous recombination, including break-induced replication repair, lead instability. Off-target especially those present S deletions gene amplifications, resulting high frequency cell lymphomas derived from cells express or have expressed AID.