Zhang Jing, Bellani Marina A, Huang Jing, James Ryan C, Pokharel Durga, Gichimu Julia, Gali Himabindu, Stewart Grant, Seidman Michael M
Department of Neurosurgery, Institute for Advanced Study, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China.
Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States.
Front Cell Dev Biol. 2021 Aug 31;9:729265. doi: 10.3389/fcell.2021.729265. eCollection 2021.
Replisomes follow a schedule in which replication of DNA in euchromatin is early in S phase while sequences in heterochromatin replicate late. Impediments to DNA replication, referred to as replication stress, can stall replication forks triggering activation of the ATR kinase and downstream pathways. While there is substantial literature on the local consequences of replisome stalling-double strand breaks, reversed forks, or genomic rearrangements-there is limited understanding of the determinants of replisome stalling vs. continued progression. Although many proteins are recruited to stalled replisomes, current models assume a single species of "stressed" replisome, independent of genomic location. Here we describe our approach to visualizing replication fork encounters with the potent block imposed by a DNA interstrand crosslink (ICL) and our discovery of an unexpected pathway of replication restart (traverse) past an intact ICL. Additionally, we found two biochemically distinct replisomes distinguished by activity in different stages of S phase and chromatin environment. Each contains different proteins that contribute to ICL traverse.
复制体遵循一种时间表，其中常染色质中的DNA复制在S期早期进行，而异染色质中的序列则在后期复制。DNA复制的障碍，即所谓的复制应激，会使复制叉停滞，触发ATR激酶和下游通路的激活。虽然有大量关于复制体停滞的局部后果——双链断裂、反向叉或基因组重排——的文献，但对于复制体停滞与继续前进的决定因素了解有限。尽管许多蛋白质被招募到停滞的复制体上，但目前的模型假设存在单一类型的“应激”复制体，与基因组位置无关。在这里，我们描述了我们可视化复制叉与DNA链间交联（ICL）施加的强大阻滞相遇的方法，以及我们发现的绕过完整ICL的意外复制重启（穿越）途径。此外，我们发现了两种在生化上不同的复制体，它们在S期的不同阶段和染色质环境中的活性不同。每种复制体都包含有助于ICL穿越的不同蛋白质。
