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Begusove, M ; Eon, S ; Sy, D ; Culard, F ; Charlier, M ; Spotheim-Maurizot, M

Radiosensitivity of DNA in a specific protein-DNA complex : the lac repressor-lac operator complex

International Journal of Radiation Biology 77 (6) 645-654

par Administrateur - publié le

Abstract :

Purpose : To calculate the probability of radiation-induced frank strand breakage (FSB) at each nucleotide in the Escherichia coli lac repressor-lac operator system using a simulation procedure. To compare calculated and experimental results. To asses the contribution of DNA conformational changes and of the masking by the protein to DNA protection by the repressor. Materials and methods : Two structures of the complex were extracted from the PDB databank : crystallography- and NMR-based structures. Calculations were made of the accessibility of the atoms mainly involved in strand breakage (H4’ and H5’) to OH* and of the FSB probabilities, along : (1) DNA in the complex ; (2) DNA in the complex depleted of the repressor ; and (3) a linear DNA having the same sequence. An 80 bp fragment bearing the operator was irradiated alone or in presence of the repressor.