RESUMO
The paper analyzes the effects of spontaneous level of yH2AX and 53BP1 foci on a frequency of radiation-induced centromere-negative and centromere-positive micronuclei in peripheral blood lymphocytes of 54 healthy individuals after exposure to 2 Gy of ionizing radiation in vitro. An inverse correlation was found between the level of spontaneous yH2AX foci and the frequency of centromere-negative micronuclei after irradiation. The corresponding correlations between the spontaneous level of protein 53BP1 foci and the frequency of centromere-negative micronuclei were not statistically significant. In addition, cells of the individuals with a high frequency of radiation-induced micronuclei were also characterized by a low proliferative activity. It was suggested that DNA double strand break repair works less efficiently in cells of the individuals with low levels of spontaneous yH2AX foci, and a greater number of DNA double strand breaks after exposure to ionizing radiation remains unrepaired, thus leading to a cell cycle block and an increase of the frequency of centromere-negative micronuclei.