Interphase chromosome locus displacement induced by low-doses of radiation

The most important stage in the making of mutations is a reparation of different DNA damage, including the more deleterious double-strand DNA breaks (DSB). The first stage of adaptive response--fundamental antimutagenic cell reaction, purposeful to reparation for induced DSB repair--is investigated in present work. Non-radioactive in situ hybridization of biotin-labeled DNA probe was used to mark chromosome 1 pericentromeric regions (PR) in G0 human lymphocytes. It was shown that under 3-10 cGy (X-radiation, 160 kV) PR become displaced from a nucleus periphery to inner territory of a nucleus. The moving process realizes during several hours after an irradiation. As far as some non-specific gene repressors are co-localized with chromosome centromeric regions it is possible hypothesizes that the displacement cause changing expression of some genes. It is possible to propose that an absence of radiation induced chromosome locus displacement may be one of causes DSB repair disturbance. This hypothesis was tested by the model. It is assumed that one consequence of the underlying defect may be inappropriate involvement of cell's recombination machinery in the repair of DSB. We studied lymphocytes of patients with hereditary BRCA2 mutation. It is thought that this gene takes part in DSB repair. The significant differences of the PR moving between control samples and the cases were revealed under 10 cGy. Similar results were observed on lymphocytes of patients with Fanconi syndrome. Thus, abnormal moving of interphase nucleus chromosomes conditioned by low-dose irradiation may suggest on imperfect machinery of DSB repair, i.e. genetic risk. We realize that further investigations are needed for definitive conclusion.