Premature condensation induces breaks at the interface of early and late replicating chromosome bands bearing common fragile sites

Abstract

Various studies suggest a tight relationship between chromosome rearrangements driving tumor progression and breaks at loci called common fragile sites. Most of these sites are induced after perturbation of the replication dynamics, notably by aphidicolin treatment. We have mapped the majority of these sites to the interface of R and G bands, which calls into question the previous assignment of aphidicolin-sensitive sites to R bands. This observation suggests that most of them correspond to loci that ensure the transition between early and late replicating domains. We show that calyculin A, which triggers chromosome condensation at any phase of the cell cycle but does not markedly impair replication, induces damage in the chromosomes of human lymphocytes treated in G 2 but not in G1 phase. We demonstrate that these lesions colocalize with those induced by aphidicolin treatment. Hence, common fragile site stability is compromised, whether aphidicolin delays replication or calyculin A advances condensation. We also show that, in cells that go through an unperturbed S phase, completion of their replication and͞or replication-associated chromatin reorganization occur all along the G2 phase, which may explain their inability to condense properly after calyculin A treatment during this phase of the cell cycle.genome instability ͉ DNA damage ͉ calyculin A ͉ aphidicolin ͉ cell cycle

Cep63 Recruits Cdk1 to the Centrosome: Implications for Regulation of Mitotic Entry, Centrosome Amplification, and Genome Maintenance

“…Finally, we show an association of Cep63 overexpression with aggressive behavior of human neuroblastomas and an impaired DNA damage response to replication stress, a condition shared by many oncogene-transformed cells and the majority of human neoplasms (37)(38)(39). The increased rate of DNA DSBs we observed in the presence of aphidicolin might be explained by elevated Cep63 causing Cdk hyperactivation and, consequently, an override of checkpoint mechanisms that normally guard against mitotic entry with unrepaired chromosomes.…”

“…In addition to Cdk-dependent centrosome amplification, Cep63-triggered Cdk deregulation might also impair the DNA damage response and lead to persistence of unrepaired replication-associated defects in the form of DNA DSBs in mitotic cells (37)(38)(39). We therefore evaluated whether DSB signaling and frequency might be enhanced in Cep63-overexpressing cells exposed to replication stress.…”

Epstein-Barr Virus BGLF4 Kinase Induces Premature Chromosome Condensation through Activation of Condensin and Topoisomerase II

“…This suggests that some cells may escape the consequences induced by BGLF4 and grow continuously. However, because premature condensation is correlated with induction of DNA breaks at replicating chromosome-bearing common fragile sites (13), it will be interesting to evaluate whether constitutive expression of a low level of BGLF4 may affect host genome stability.…”

Visualize Dynamic Chromosome

“…These drawbacks of the conventional PCC technique have been recently overcome with a much easier and more rapid technique using calyculin A or okadaic acid, specific inhibitors of protein phosphatases (drug-induced PCC technique) (Gotoh et al, 1995;Gotoh and Asakawa, 1996;Asakawa and Gotoh, 1997;Durante et al, 1998;Gotoh and Durante, 2006). Drug-induced PCC is becoming now 'popular' and has been used in a wide range of cytogenetic applications (Gotoh and Asakawa, 1996;Asakawa and Gotoh, 1997;Gotoh et al, 1999;Ito et al, 2002;Terzoudi et al, 2003;El Achkar et al, 2005;Srebniak et al, 2005;Terzoudi et al, 2005;Deckbar et al, 2007;Gotoh, 2007;Beucher et al, 2009;van Harn et al, 2010). Thus, drug-induced PCC technique is suitable to visualize dynamic chromosomes particularly in interphase nuclei.…”