Chromosomal aberration dynamics through the cell cycle.

DNA double-strand breaks are the crucial lesions underlying the formation of chromosomal aberrations, their formation and kinetics have been extensively studied, although dynamics of the repair process has not been fully understood. By using a combination of different cytogenetic techniques to analyze cells in G0, G2 and M phase, in the present study we perform a follow up study of the dynamics of different radiation induced chromosomal aberrations. Data here presented show that in G0 phase chromosome fragments lacking telomere signals (incomplete chromosome elements, ICE) show a slow repair, but when repair occurs tend to reconstitute the original chromosomes, and those that do not repair seem to be selected by interphase cell death and cell cycle checkpoints. In contrast, complete chromosome aberrations, as dicentrics, show a very fast formation kinetics. Similar frequencies of dicentrics were observed in G0, G2 and M cells, indicating that this chromosome-type of aberration can progress through the cell cycle without negative selection. Our study reinforce the hypothesis that ICE are strongly negatively selected from G2 to M phase. However, the G2/M checkpoint seems to be not involved in this selection. The ICE frequencies observed after G2/M abrogation by caffeine are similar to the ones without abrogation, and clearly lower to the ones observed in G2.