Chromosome dynamics and cyclic change of cell life and death

Ouchi, Noriyuki

Radiation sensitivity via cell survival shows cyclic radiation response, i.e. minimal when cells are irradiated in the early post-mitotic (G1) and the pre-mitotic (G2) phases of the cell cycle, and maximal in the mitotic (M) phase and late G1 or early synthesis (S) phases. Origin of the cell-cycle dependent radiation sensitivity is supposed to be a consequence of some intra-cellular dynamics, e.g. regulation mechanism of cell-cycle checkpoint, repair ability of DNA damage and higher order structure of chromosomes, no explicit theoretical explanation exists on this cyclic response yet. Here, cell-cycle dependent radiation sensitivity is studied from the viewpoints of dynamical aspects of chromosome in association with its cell-cycle dependent structural changes. For this purpose, dynamical model of chromosome is mathematically constructed based on the elastic nature of chromosomes and its radiation effects are simulated by introducing DNA double strand break (DSB) to the model.