小柯机器人

美国宾夕法尼亚大学Roger A. Greenberg小组发现，断裂诱导的复制协调切除依赖的模板切换。相关论文于2023年6月14日在线发表在《自然》杂志上。

研究人员表示，断裂诱导端粒合成（BITS）是一种与RAD51无关的断裂诱导复制形式，有助于端粒的可变延长。这种同源导向的修复机制利用由增殖细胞核抗原（PCNA）和DNA聚合酶-δ组成的最小复制体，在数千碱基上执行保守的DNA修复合成。这种长距离的同源重组修复合成如何应对引起复制压力的复杂二级DNA结构仍不清楚。此外，断裂诱导的复制体是否会协调额外的DNA修复事件以确保进程性也不清楚。

研究人员将同步双链断裂诱导与分离的染色质片段（PICh）的蛋白质组学相结合，以捕捉BITS期间端粒DNA损伤反应的蛋白质组。这种方法揭示了以复制应激为主的反应，突出表现为通过RAD18依赖的PCNA泛素化，修复合成驱动的DNA损伤耐受信号。此外，SNM1A核酸酶被确定为泛素化PCNA依赖的DNA损伤耐受的主要效应器。SNM1A在受损的端粒上识别泛素修饰的断裂诱导复制体，这引导其核酸酶活性促进切除。这些发现表明，断裂诱导的复制协调了切除依赖性病变的旁路，SNM1A的核酸酶活性是哺乳动物细胞中泛素化PCNA指导重组的一个关键效应器。

附：英文原文

Title: Break-induced replication orchestrates resection-dependent template switching

Author: Zhang, Tianpeng, Rawal, Yashpal, Jiang, Haoyang, Kwon, Youngho, Sung, Patrick, Greenberg, Roger A.

Issue&Volume: 2023-06-14

Abstract: Break-induced telomere synthesis (BITS) is a RAD51-independent form of break-induced replication that contributes to alternative lengthening of telomeres1,2. This homology-directed repair mechanism utilizes a minimal replisome comprising proliferating cell nuclear antigen (PCNA) and DNA polymerase-δ to execute conservative DNA repair synthesis over many kilobases. How this long-tract homologous recombination repair synthesis responds to complex secondary DNA structures that elicit replication stress remains unclear3–5. Moreover, whether the break-induced replisome orchestrates additional DNA repair events to ensure processivity is also unclear. Here we combine synchronous double-strand break induction with proteomics of isolated chromatin segments (PICh) to capture the telomeric DNA damage response proteome during BITS1,6. This approach revealed a replication stress-dominated response, highlighted by repair synthesis-driven DNA damage tolerance signalling through RAD18-dependent PCNA ubiquitination. Furthermore, the SNM1A nuclease was identified as the major effector of ubiquitinated PCNA-dependent DNA damage tolerance. SNM1A recognizes the ubiquitin-modified break-induced replisome at damaged telomeres, and this directs its nuclease activity to promote resection. These findings show that break-induced replication orchestrates resection-dependent lesion bypass, with SNM1A nuclease activity serving as a critical effector of ubiquitinated PCNA-directed recombination in mammalian cells. Break-induced telomere synthesis initiates recruitment of the SNM1A nuclease, which promotes DNA end resection that in turn allows template switching to enable bypass of lesions.

DOI: 10.1038/s41586-023-06177-3

Source: https://www.nature.com/articles/s41586-023-06177-3

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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