Segmentation of human chromosomes induced by 5-ACR (5-azacytidine).

The 5-ACR (5-azacytidine) introduced in human lymphocyte cultures induces a lack or a delay of condensation of some chromosome segments corresponding to the G-bands. The resulting R-banding is very similar to that obtained with a 7-h treatment by BrdU, although the segmentation may be much stronger (pulverization) with high doses. However, the 5-ACR does not induce chromatid asymmetry, as BrdU does. This constitutes a new argument for considering that the segmentation and the asymmetry of chromatids depend, at least partly, on two different mechanisms, where proteins are probably involved. Another effect of 5-ACR is to increase chromosome associations by satellites, secondary constrictions, and telomeric regions.