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XB-ART-57746
Mol Cell 2021 Mar 18;816:1309-1318.e6. doi: 10.1016/j.molcel.2020.12.039.
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Single-strand DNA breaks cause replisome disassembly.

Vrtis KB , Dewar JM , Chistol G , Wu RA , Graham TGW , Walter JC .


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DNA damage impedes replication fork progression and threatens genome stability. Upon encounter with most DNA adducts, the replicative CMG helicase (CDC45-MCM2-7-GINS) stalls or uncouples from the point of synthesis, yet eventually resumes replication. However, little is known about the effect on replication of single-strand breaks or "nicks," which are abundant in mammalian cells. Using Xenopus egg extracts, we reveal that CMG collision with a nick in the leading strand template generates a blunt-ended double-strand break (DSB). Moreover, CMG, which encircles the leading strand template, "runs off" the end of the DSB. In contrast, CMG collision with a lagging strand nick generates a broken end with a single-stranded overhang. In this setting, CMG translocates along double-stranded DNA beyond the break and is then ubiquitylated and removed from chromatin by the same pathway used during replication termination. Our results show that nicks are uniquely dangerous DNA lesions that invariably cause replisome disassembly, and they suggest that CMG cannot be stored on dsDNA while cells resolve replication stress.

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Species referenced: Xenopus laevis
Genes referenced: mcm2
GO keywords: DNA repair [+]


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References [+] :
Caldecott, Single-strand break repair and genetic disease. 2008, Pubmed