UNTANGLING THE ROLE OF DNA TOPOISOMERASE-II IN MITOTIC CHROMOSOME STRUCTURE AND FUNCTION

DNA topoisomerase II (topo II) is involved in chromosome structure and function, although its exact location and role in mitosis are somewha t controversial. This is due in part to the varied reports of its loca lization on mitotic chromosomes, which has been described at different times as uniformly distributed, axial on the chromosome arms and pred ominantly centromeric. These disparate results are probably due to sev eral factors, including use of different preparation and fixation tech niques, species differences and changes in distribution during the cel l cycle. Recently, several papers have re-investigated the distributio n of topo II on chromosomes as a function of cell cycle and species((1 -3)). The new studies suggest that Topo II has a dynamic pattern of di stribution on the chromosomes, in general becoming axial as chromosome s condense during prophase and then concentrating at centromeres durin g metaphase. These experiments suggest a novel role for topo II in cen tromere structure and function.