Nucleic Acids Research Advance Access published online on July 13, 2009
Nucleic Acids Research, doi:10.1093/nar/gkp582
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Genome Integrity, Repair and Replication |
Stabilization of quadruplex DNA perturbs telomere replication leading to the activation of an ATR-dependent ATM signaling pathway
1Department of Experimental Chemotherapy, Regina Elena Cancer Institute, Via delle Messi d’Oro 156, 00158 Rome, Italy, 2Laboratory of Molecular Biology of the Cell, CNRS, Ecole Normale Supérieure de Lyon, UMR5239, IFR128, 46 allée d'Italie, 69364 Lyon, France, 3Center for Biomolecular Sciences, School of Pharmacy, University of Nottingham, University Park, NG7 2RD Nottingham, UK and 4Department of Oncology, Pharmacological Research Institute ‘Mario Negri’, Via La Masa 19, 20156 Milan, Italy
*To whom correspondence should be addressed. Tel: +39 06 52662569; Fax: +39 06 52662505; Email: biroccio{at}ifo.it
Received May 20, 2009. Revised June 19, 2009. Accepted June 24, 2009.
Functional telomeres are required to maintain the replicative ability of cancer cells and represent putative targets for G-quadruplex (G4) ligands. Here, we show that the pentacyclic acridinium salt RHPS4, one of the most effective and selective G4 ligands, triggers damages in cells traversing S phase by interfering with telomere replication. Indeed, we found that RHPS4 markedly reduced BrdU incorporation at telomeres and altered the dynamic association of the telomeric proteins TRF1, TRF2 and POT1, leading to chromosome aberrations such as telomere fusions and telomere doublets. Analysis of the molecular damage pathway revealed that RHPS4 induced an ATR-dependent ATM signaling that plays a functional role in the cellular response to RHPS4 treatment. We propose that RHPS4, by stabilizing G4 DNA at telomeres, impairs fork progression and/or telomere processing resulting in telomere dysfunction and activation of a replication stress response pathway. The detailed understanding of the molecular mode of action of this class of compounds makes them attractive tools to understand telomere biology and provides the basis for a rational use of G4 ligands for the therapy of cancer.