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Interactions de la région C-terminale de MLH1 nécessaires à la voie de réparation des mésappariements de l'ADN

Abstract : Eucaryotic Mlh1 is a core component of mismatch repair pathway (MMR). In yeast organisms, Mlh1 forms heterodimer with its C-terminal region with endonucleases Pms1 and Mlh3. The C-terminal region of Mlh1 is also involved in interactions with MMR exonuclease Exo1 and two proteins, Ntg2 and Sgs1, which are involved in other DNA repair pathways. First, we identified and charaterised the interaction site between Mlh1 and proteins Exo1, Ntg2, and Sgs1, that share the same motif of 5 amino acids, (R/K)SK(Y/F)F, named MIP box for Mlh1 Interacting Protein. We showed that these 3 proteins bind to the same site, named site S2. 10 positions of Mlh1 important for interactions on site S2 were identified and a micromolar affinity was measured by calorimetry between the C-terminal region of Mlh1 and peptides containing a MIP box. We showed that human EXO1 and BLM specifically with human MLH1 through their MIP box. Secondly, we solved the X-ray structure of the C-terminal region of Mlh1*Pms1 heterodimer at 2.6Å. The structure shows that the surface buried upon heterodimerisation is higher in eucaryotes than in MutL homodimers. The structure confirms the overall structure of the site S2 predicted in the first part of this study. The endonuclease site of Pms1 presents in the crystal two zinc atoms that are bound by five Pms1 residues and the last residue of Mlh1 chain, cystein C769. This structure represents the first image of the C-terminal region of an eucaryote Mlh1*Pms1 heterodimer. It allows localizing the positions of human MLH1 mutants associated with colon cancers named HNPCC.
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Submitted on : Tuesday, October 4, 2011 - 5:21:00 PM
Last modification on : Friday, June 12, 2020 - 8:31:26 PM
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  • HAL Id : tel-00628928, version 1




Emeric Gueneau. Interactions de la région C-terminale de MLH1 nécessaires à la voie de réparation des mésappariements de l'ADN. Sciences agricoles. Université Paris Sud - Paris XI, 2011. Français. ⟨NNT : 2011PA114804⟩. ⟨tel-00628928⟩



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