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Bruno T.,Regina Elena Cancer Institute | Desantis A.,Regina Elena Cancer Institute | Desantis A.,University of LAquila | Bossi G.,Regina Elena Cancer Institute | And 16 more authors.
Cancer Cell | Year: 2010

Che-1 is a RNA polymerase II binding protein involved in the regulation of gene transcription and, in response to DNA damage, promotes p53 transcription. In this study, we investigated whether Che-1 regulates mutant p53 expression. We found that Che-1 is required for sustaining mutant p53 expression in several cancer cell lines, and that Che-1 depletion by siRNA induces apoptosis both in vitro and in vivo. Notably, loss of Che-1 activates DNA damage checkpoint response and induces transactivation of p73. Therefore, these findings underline the important role that Che-1 has in survival of cells expressing mutant p53. © 2010 Elsevier Inc. Source


Basile G.,Italy Genome Stability Group | Leuzzi G.,Italy Genome Stability Group | Pichierri P.,Genome Stability Group | Franchitto A.,Italy Genome Stability Group
Nucleic acids research | Year: 2014

Werner syndrome (WS) is a human chromosomal instability disorder associated with cancer predisposition and caused by mutations in the WRN gene. WRN helicase activity is crucial in limiting breakage at common fragile sites (CFS), which are the preferential targets of genome instability in precancerous lesions. However, the precise function of WRN in response to mild replication stress, like that commonly used to induce breaks at CFS, is still missing. Here, we establish that WRN plays a role in mediating CHK1 activation under moderate replication stress. We provide evidence that phosphorylation of CHK1 relies on the ATR-mediated phosphorylation of WRN, but not on WRN helicase activity. Analysis of replication fork dynamics shows that loss of WRN checkpoint mediator function as well as of WRN helicase activity hamper replication fork progression, and lead to new origin activation to allow recovery from replication slowing upon replication stress. Furthermore, bypass of WRN checkpoint mediator function through overexpression of a phospho-mimic form of CHK1 restores fork progression and chromosome stability to the wild-type levels. Together, these findings are the first demonstration that WRN regulates the ATR-checkpoint activation upon mild replication stress, preventing chromosome fragility. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research. Source


Franchitto A.,Section of Molecular Epidemiology | Franchitto A.,Genome Stability Group | Pichierri P.,Section of Experimental and Computational Carcinogenesis | Pichierri P.,Genome Stability Group
Cellular and Molecular Life Sciences | Year: 2014

The acquisition of genomic instability is a triggering factor in cancer development, and common fragile sites (CFS) are the preferential target of chromosomal instability under conditions of replicative stress in the human genome. Although the mechanisms leading to CFS expression and the cellular factors required to suppress CFS instability remain largely undefined, it is clear that DNA becomes more susceptible to breakage when replication is impaired. The models proposed so far to explain how CFS instability arises imply that replication fork progression along these regions is perturbed due to intrinsic features of fragile sites and events that directly affect DNA replication. The observation that proteins implicated in the safe recovery of stalled forks or in engaging recombination at collapsed forks increase CFS expression when downregulated or mutated suggests that the stabilization and recovery of perturbed replication forks are crucial to guarantee CFS integrity. © 2014 Springer Basel. Source


Pichierri P.,Genome Stability Group | Ammazzalorso F.,Genome Stability Group | Bignami M.,Section of Experimental and Computational Carcinogenesis | Franchitto A.,Genome Stability Group
Aging | Year: 2011

The Werner syndrome protein (WRN) is a member of the human RecQ family DNA helicases implicated in the maintenance of genome stability. Loss of WRN gives rise to the Werner syndrome, a genetic disease characterised by premature aging and cancer predisposition. WRN plays a crucial role in the response to replication stress and significantly contributes to the recovery of stalled replication forks, although how this function is regulated is not fully appreciated. There is a growing body of evidence that WRN accomplishes its task in close connection with the replication checkpoint. In eukaryotic cells, the replication checkpoint response, which involves both the ATR and ATM kinase activities, is deputed to the maintenance of fork integrity and re-establishment of fork progression. Our recent findings indicate that ATR and ATM modulate WRN function at defined steps of the response to replication fork arrest. This review focuses on the novel evidence of a functional relationship between WRN and the replication checkpoint and how this cross-talk might contribute to prevent genome instability, a common feature of senescent and cancer cells. © Pichierri. Source


Franchitto A.,Genome Stability Group | Pichierri P.,Genome Stability Group
Cell Cycle | Year: 2011

Common fragile sites (CFS) are difficult-to-replicate genomic regions that show a high propensity to breakage following certain forms of DNA replication stress. Long considered a fascinating component of human chromosome structure, their relevance for biology is proven by the fact that they are frequently rearranged in cancer cells. Furthermore, CFS were found to be the preferential targets for genome instability in the early stages of human tumorigenesis. In recent years, much progress has been made in understanding the structural features of CFS and the mechanisms that monitor and regulate their integrity. From these studies, it has emerged that their fragility may depend on the abnormally high frequency of fork-stalling events occurring at CFS during DNA replication. Consistently, the ATR-dependent checkpoint together with several proteins involved in response to replication fork stalling have been implicated in maintaining CFS stability. Furthermore, more recent findings propose that the scarcity of replication initiation events within CFS may contribute to their expression upon replication perturbation. This review will focus on the molecular determinants responsible for genomic instability at CFS and the systems used by cells to address this eventuality. © 2011 Landes Bioscience. Source

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