Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Cell. 2024 Oct 17;187(21):6055-6070.e22. doi: 10.1016/j.cell.2024.08.001. Epub 2024 Aug 23.
Chromothripsis describes the catastrophic shattering of mis-segregated chromosomes trapped within micronuclei. Although micronuclei accumulate DNA double-strand breaks and replication defects throughout interphase, how chromosomes undergo shattering remains unresolved. Using CRISPR-Cas9 screens, we identify a non-canonical role of the Fanconi anemia (FA) pathway as a driver of chromothripsis. Inactivation of the FA pathway suppresses chromosome shattering during mitosis without impacting interphase-associated defects within micronuclei. Mono-ubiquitination of FANCI-FANCD2 by the FA core complex promotes its mitotic engagement with under-replicated micronuclear chromosomes. The structure-selective SLX4-XPF-ERCC1 endonuclease subsequently induces large-scale nucleolytic cleavage of persistent DNA replication intermediates, which stimulates POLD3-dependent mitotic DNA synthesis to prime shattered fragments for reassembly in the ensuing cell cycle. Notably, FA-pathway-induced chromothripsis generates complex genomic rearrangements and extrachromosomal DNA that confer acquired resistance to anti-cancer therapies. Our findings demonstrate how pathological activation of a central DNA repair mechanism paradoxically triggers cancer genome evolution through chromothripsis.
染色体重排描述了被错误分离的染色体被困在微核内的灾难性碎裂。尽管微核在整个间期积累 DNA 双链断裂和复制缺陷，但染色体如何发生碎裂仍未得到解决。使用 CRISPR-Cas9 筛选，我们发现范可尼贫血（FA）途径的非典型作用是染色体重排的驱动因素。FA 途径的失活抑制了有丝分裂期间的染色体碎裂，而不影响微核内与间期相关的缺陷。FA 核心复合物对 FANCI-FANCD2 的单泛素化促进了其在有丝分裂期间与复制不足的微核染色体的结合。随后，结构选择性的 SLX4-XPF-ERCC1 内切酶诱导大量大规模的核酶切割持续的 DNA 复制中间体，刺激 POLD3 依赖性有丝分裂 DNA 合成，为随后的细胞周期中重新组装碎裂的片段做好准备。值得注意的是，FA 途径诱导的染色体重排会产生复杂的基因组重排和染色体外 DNA，从而赋予对癌症治疗的获得性耐药性。我们的研究结果表明，中央 DNA 修复机制的病理性激活如何通过染色体重排引发癌症基因组的进化。
