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Étude de MutS à l'échelle de la molécule unique

Abstract : Using single molecule micromanipulation and force measurement on DNA with a magnetic tweezer setup, this work has been devoted in part to a study of the " long patch " repair system of DNA. This repair involves the MutS, MutH and MutL proteins, and uses an as yet unidentified mechanism in order to act at a distance, between a site of mismatch (due for example to a replication error), and a proximal GATC hemimethylation
site, so that the repair is directed toward the newly synthesized strand. Some models of this action at a distance, involve the presence of a DNA loop, induced by the action of MutS on a mismatch. We have tried to explore this possibility, by studying the mechanical behavior of a long double stranded DNA, containing (or not containing) a mismatch. We have not detected any specific loop formation in DNA, i.e. only induced when a mismatch is present. This negative result seems to exclude specific loop formation induced by MutS. In a second part, we have studied the mechanical behavior of a Holliday junction (a cross-shaped DNA, involved as an intermediate during recombination). We have shown directly that it is possible to extrude a Holliday junction, by mechanically undercoiling a palindromic DNA. We have deduced the pitch of the DNA double helix from the behavior of the Holliday junction. In a last part, we have studied the influence of Ethidium Bromide, on DNA. We have shown that this intercalating agent is able to induce a non-specific attraction either intra-strand or inter-strand, in single-stranded DNA.
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Submitted on : Thursday, November 8, 2007 - 9:31:52 AM
Last modification on : Thursday, December 10, 2020 - 12:36:18 PM
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  • HAL Id : tel-00186125, version 1

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Fabien Guillemot. Étude de MutS à l'échelle de la molécule unique. Biophysique [physics.bio-ph]. Université Paris-Diderot - Paris VII, 2007. Français. ⟨tel-00186125⟩

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