RPDOC - Retour Post-Doctorants

DNA dynamics and genome integrity – DNA dyna

Submission summary

The genome is constantly damaged by a variety of exogenous and endogenous agents. Among the various forms of DNA damage, double-strand breaks (DSBs) are the most cytotoxic and genotoxic for the cell (Wyman and Kanaar, 2006, Agarwal et al., 2006). Failure to repair such lesions leads to genomic instability or cell death. In higher eukaryotes, mutations in DNA repair genes lead to cancer predisposition (Rassool, 2003, Thorslund and West, 2007, Van Gent et al., 2001).

In response to DSBs, DNA repair proteins relocolize from diffuse nuclear distribution to distinct sub-nuclear foci at the place of the break (Lisby et al., 2004). Despite a large literature describing DNA repair and homologous recombination, the fine structure and the dynamics of these recombination foci remains unknown. In addition to the formation of repair foci, recent evidence shows that the mobility of DNA is dramatically increased in the presence of DSBs (Mine-Hattab and Rothstein, 2012, Krawczyk et al., 2012, Dion et al., 2012). Increased DNA mobility could potentially lead to unwanted chromosomal rearrangements, however, the role of DNA dynamics in maintaining genome integrity has not been elucidated.
This project is divided into 3 parts that each will examine a different aspect of homologous recombination in vivo using advanced single molecule techniques.

1. In the first part of the project, we will characterize the molecular properties of repair foci using photo-activable localization microscopy (PALM). First, we will examine if there is a sub-structure inside repair foci. Next, we will characterize the mobility of repair proteins in the presence and in the absence of DSB. Finally, we will examine how mutations known to be defective in homologous recombination affect the internal structure and the dynamics of repair foci.

2. In the second part of the project, we propose to examine the mechanisms that control DNA dynamics inside the nucleus using in vivo single particle tracking of DNA loci. In particular, we ask which genes control the DNA dynamics in the presence and in the absence of DSBs. Malfunctioning of these genes might promote unwanted rearrangements and endanger genome stability. Finally, we will examine the influence of aneuploidy in DNA dynamics.

3. In the third part of the project, we will focus on a recent anti-cancer molecule called Dbait. Dbait are short inhibiting DNA molecules that can mimic DSBs without creating any physical break in the genome (Quanz et al., 2009a). Because they are recognized as DSB by the cell, they over-activate the DNA repair checkpoint responses and enhance the efficacity of radio or chemo-therapies (Quanz et al., 2009b, Devun et al., 2011). Those molecules are currently under clinical trials in combination with classical chemio-therapy to treat resistant tumors. Here, we will characterize the DNA dynamics in the presence of Dbait molecules.Ultimately, we aim to optimize the use of Dbait molecules to minimize the risk to compromise the genome integrity.

In the first two parts of the project, we will use budding yeast as a model system as this organism is a powerful genetic system for studying the cellular response to DNA damage. Our goal is to transpose our studies to human cells and we will begin this transposition with the third part of the project.

The host laboratory for this research is at the « Ecole Normale Superieure de Paris » directed by Xavier Darzacq, a pionner in in vivo super-resolution microscopy. He is interested in broadening his research to the problem of DNA repair and DNA dynamics. Finally, thanks to a collaboration with Marie Dutreix and the DNA therapeutic company, the project will be a great opportunity to strengthen the connections between fundamental research and medical applications.

Project coordination

Judith MINÉ-HATTAB (Institut Curie) – judith.hattab.mine@gmail.com

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IC Institut Curie

Help of the ANR 347,702 euros
Beginning and duration of the scientific project: February 2013 - 36 Months

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