Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, San Diego, United States.
Departments of Medicine, University of California School of Medicine, San Diego, San Diego, United States.
Elife. 2020 Aug 7;9:e58223. doi: 10.7554/eLife.58223.
Foldback inversions, also called inverted duplications, have been observed in human genetic diseases and cancers. Here, we used a genetic system that generates gross chromosomal rearrangements (GCRs) mediated by foldback inversions combined with whole-genome sequencing to study their formation. Foldback inversions were mediated by formation of single-stranded DNA hairpins. Two types of hairpins were identified: small-loop hairpins that were suppressed by , , , and and large-loop hairpins that were suppressed by , , , and . Analysis of CRISPR/Cas9-induced double strand breaks (DSBs) revealed that long-stem hairpin-forming sequences could form foldback inversions when proximal or distal to the DSB, whereas short-stem hairpin-forming sequences formed foldback inversions when proximal to the DSB. Finally, we found that foldback inversion GCRs were stabilized by secondary rearrangements, mostly mediated by different homologous recombination mechanisms including single-strand annealing; however, -dependent break-induced replication did not appear to be involved forming secondary rearrangements.
回文倒位，也称为倒位重复，已在人类遗传疾病和癌症中观察到。在这里，我们使用了一种通过回文倒位产生的遗传系统，该系统介导的染色体大片段重排（GCR）与全基因组测序相结合，以研究其形成机制。回文倒位是由单链 DNA 发夹的形成介导的。鉴定出两种类型的发夹：被 、 、 和 抑制的小环发夹，以及被 、 、 和 抑制的大环发夹。对 CRISPR/Cas9 诱导的双链断裂（DSB）的分析表明，长茎发夹形成序列在 DSB 近端或远端时可以形成回文倒位，而短茎发夹形成序列在 DSB 近端时可以形成回文倒位。最后，我们发现回文倒位 GCRs 可以通过次级重排稳定，这些次级重排主要由不同的同源重组机制介导，包括单链退火；然而，似乎不涉及形成次级重排的 - 依赖性断裂诱导复制。
