Xu Yuanlin, Morrow Carl A, Laksir Yassine, Holt Orla M, Taylor Kezia, Tsiappourdhi Costas, Collins Patrick, Jia Su, Andreadis Christos, Whitby Matthew C
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Mol Cell. 2025 Jan 2;85(1):91-106.e5. doi: 10.1016/j.molcel.2024.10.026. Epub 2024 Nov 18.
Encounters between replication forks and unrepaired DNA single-strand breaks (SSBs) can generate both single-ended and double-ended double-strand breaks (seDSBs and deDSBs). seDSBs can be repaired by break-induced replication (BIR), which is a highly mutagenic pathway that is thought to be responsible for many of the mutations and genome rearrangements that drive cancer development. However, the frequency of BIR's deployment and its ability to be triggered by both leading and lagging template strand SSBs were unclear. Using site- and strand-specific SSBs generated by nicking enzymes, including CRISPR-Cas9 nickase (Cas9n), we demonstrate that leading and lagging template strand SSBs in fission yeast are typically converted into deDSBs that are repaired by homologous recombination. However, both types of SSBs can also trigger BIR, and the frequency of these events increases when fork convergence is delayed and the non-homologous end joining protein Ku70 is deleted.
复制叉与未修复的DNA单链断裂（SSB）相遇可产生单端和双端双链断裂（seDSB和deDSB）。seDSB可通过断裂诱导复制（BIR）进行修复，这是一种高度诱变的途径，被认为与许多驱动癌症发展的突变和基因组重排有关。然而，BIR的使用频率及其被前导链和后随链模板链SSB触发的能力尚不清楚。我们使用包括CRISPR-Cas9切口酶（Cas9n）在内的切口酶产生的位点特异性和链特异性SSB，证明裂殖酵母中的前导链和后随链模板链SSB通常会转化为通过同源重组修复的deDSB。然而，这两种类型的SSB也都可以触发BIR，当叉汇合延迟且非同源末端连接蛋白Ku70缺失时，这些事件的频率会增加。
