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Séminaire MCBT

Mardi 24 juin 2014 à 11h00,
Salle Louis Weil, E424

Orateur : Giovanni Cappello (LIPHY)
"Dynamics and thermodynamics of Homologous Recombination"

Abstract

Double strand damages may be very harmful for the genome integrity. As they often involve a loss of genetic information, a simple end to end joining would introduce severe deletion or mutations on the chromosome. In order to avoid such unfortunate event, the cell uses the homologous chromosome (or the sister chromatid) as a template to reconstitute the defective DNA. This mechanism is called “Homologous Recombination”.

Homologous Recombination is among the most complex enzymatic reactions. Several partners are involved, at least one dsDNA and one ssDNA molecules, the Rad51 protein and a given amount of ATP. In addition the DNA molecules are long helices with specific sequences, they are entangled during the homology search and Rad51 acts cooperatively to catalyze the reaction. Thus, Homologous Recombination escapes the classic methods of enzymology.

To investigate the mechano-chemical aspects of Homologous Recombination, we choose the single molecule approach. We use a new type of magnetic tweezers to hold the intact DNA molecule during the whole reaction. Our system allows us to monitor the torsion and the elongation of the DNA molecule, as well as the applied stretching force and the torque exerted by the recombinase enzyme hRad51. Is such a way, we determine the Energy Landscape during the Homologous Recombination process and how it drives the reaction.

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