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PLoS One April 15, 2011; 6 (4): e18554.

Replication-fork stalling and processing at a single psoralen interstrand crosslink in Xenopus egg extracts.

Le Breton C , Hennion M , Arimondo PB , Hyrien O .

Interstrand crosslink (ICL)-inducing agents block the separation of the two DNA strands. They prevent transcription and replication and are used in clinics for the treatment of cancer and skin diseases. Here, we have introduced a single psoralen ICL at a specific site in plasmid DNA using a triplex-forming-oligonucleotide (TFO)-psoralen conjugate and studied its repair in Xenopus egg extracts that support nuclear assembly and replication of plasmid DNA. Replication forks arriving from either side stalled at the psoralen ICL. In contrast to previous observations with other ICL-inducing agents, the leading strands advanced up to the lesion without any prior pausing. Subsequently, incisions were introduced on one parental strand on both sides of the ICL. These incisions could be detected whether one or both forks reached the ICL. Using small molecule inhibitors, we found that the ATR-Chk1 pathway, but not the ATM-Chk2 pathway, stimulated both the incision step and the subsequent processing of the broken replication intermediates. Our results highlight both similarities and differences in fork stalling and repair induced by psoralen and by other ICL-forming agents.

PubMed ID: 21525992
PMC ID: PMC3078125
Article link: PLoS One

Species referenced: Xenopus
Genes referenced: atm atr chek1 chek2 rasl12 xpo5 xpo6

Article Images: [+] show captions
References [+] :
Angelov, Generation of DNA interstrand cross-links by post-synthetic reductive amination. 2009, Pubmed