研究人员利用CRISPR/Cas9核酸酶研究了复制机器与单链断裂（最常见的内源性DNA损伤形式之一）之间的相互作用。研究人员发现，前导链切口处的复制叉崩溃会产生被切除的单端双链断裂（seDSB），并通过同源重组（HR）进行修复。如果这些seDSB没有得到及时修复，相邻叉的到达就会产生双端DSB（deDSB），这可能会导致HR缺陷癌症中的基因组瘢痕。
当复制叉绕过滞后链缺口时，也会直接产生deDSB。与不依赖于复制产生的deDSB不同，缺口诱导的se/deDSB的末端切除是不依赖于BRCA1的。然而，BRCA1可拮抗53BP1对RAD51丝形成的抑制。这些结果突显了维持复制叉稳定性的独特机制。
附：英文原文
Title: Structure and repair of replication-coupled DNA breaks
Author: Raphael Pavani, Veenu Tripathi, Kyle B. Vrtis, Dali Zong, Raj Chari, Elsa Callen, Ajith V. Pankajam, Gang Zhen, Gabriel Matos-Rodrigues, Jiajie Yang, Shuheng Wu, Giordano Reginato, Wei Wu, Peter Cejka, Johannes C. Walter, André Nussenzweig
Issue&Volume: 2024-06-20
Abstract: Using CRISPR/Cas9 nicking enzymes, we examine the interaction between the replication machinery and single strand breaks, one of the most common forms of endogenous DNA damage. We show that replication fork collapse at leading strand nicks generates resected single-ended double-strand breaks (seDSBs) that are repaired by homologous recombination (HR). If these seDSBs are not promptly repaired, arrival of adjacent forks creates double ended DSBs (deDSBs), which could drive genomic scarring in HR-deficient cancers. deDSBs can also be generated directly when the replication fork bypasses lagging strand nicks. Unlike deDSBs produced independently of replication, end-resection at nick-induced se/deDSBs is BRCA1-independent. Nevertheless, BRCA1 antagonizes 53BP1 suppression of RAD51 filament formation. These results highlight unique mechanisms that maintain replication fork stability.
DOI: ado3867
Source: https://www.science.org/doi/10.1126/science.ado3867