Pathology of DNA Replication

Genetic instability is a major feature of tumor cells and it is associated with the process of carcinogenesis in humans. In many cases such instability occurs during the S phase and is due to defects in DNA replication. The enzymatic replication machinery used to copy and replicate DNA faithfully is called the replisome. Replisome progression is subjected to many control systems since its perturbation can produce changes in the genome. However, DNA duplication can be hindered by obstacles that slow, stop temporarily or completely block the replisome. Barriers hindering the progress of replication forks can have different origins: a) secondary structures in DNA, b) DNAprotein complexes, c) chromatin modifications, and d) DNA lesions. If these stalled replication forks are not resolved, chromosomal rearrangements (translocations, inversions or deletions) may occur and contribute to early stages of carcinogenesis. Thus, we think that it is important to better understand these aspects of DNA replication, both in terms of mechanisms of appearance of such obstacles and of their functional consequences.

Our experimental work aims to identifying the molecular mechanisms of replicative stress induced by arrested replication forks, using cultured human and avian cells model systems. For this purpose, we shall use technologies such as ChIP‐on‐chip and high‐throughput sequencing. This should allow us to locate the sites of replication fork obstruction at the level of entire genomes. In the long term, our work should enable us to better understand how defects caused by réplication fork stops can contribute to the development of cancers and of other genetic diseases associated with genomic instability.

Summary of main achievements
Giuseppe Baldacci : We found that homologous recombination can restart blocked replication forks, but at the expense of genome rearrangements generated by polymerase template exchange.
We showed that, in vitro, ssDNA binding proteins unwind the newly synthesized double‐stranded DNA and eliminate the impediment to polymerase passage associated with CAG/CTG triplet repeats.

Jean-Charles Cadoret : We performed the first genome‐wide analysis in human cells identifying links between human replication origins and gene expression signals.

Selection of Publications

Delagoutte E, Heneman-Masurel A, Baldacci G. 
Single-stranded DNA binding proteins unwind the newly synthesized double-stranded DNA of model miniforks.
Biochemistry 2011 50:932-944
Abstract

Lambert S, Mizuno K, Blaisonneau J, Martineau S, Chanet R, Fréon K, Murray JM, Carr AM, Baldacci G.
Homologous recombination restarts blocked replication forks at the expense of genome rearrangements by template exchange.
Mol Cell 2010 39:346-359.
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Mizuno K, Lambert S, Baldacci G, Murray JM, Carr AM.
Nearby inverted repeats fuse to generate acentric and dicentric palindromic chromosomes by a replication template exchange mechanism.
Genes Dev. 2009 Dec 15;23(24):2876-86
Abstract

Necsulea A, Guillet C, Cadoret JC, Prioleau MN, Duret L.
The relationship between DNA replication and human genome organization.
Mol Biol Evol. 2009 Apr;26(4):729-41
Abstract

Cadoret JC, Meisch F, Hassan-Zadeh V, Luyten I, Guillet C, Duret L, Quesneville H, Prioleau MN.
Genome-wide studies highlight indirect links between human replication origins and gene regulation.
Proc Natl Acad Sci U S A. 2008 Oct 14;105(41):15837-42
Abstract

Last modified 01/ 4/2012

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