TOPOISOMERASE-II-ALPHA IS ASSOCIATED WITH THE MAMMALIAN CENTROMERE INA CELL-CYCLE AND SPECIES-SPECIFIC MANNER AND IS REQUIRED FOR PROPER CENTROMERE KINETOCHORE STRUCTURE/

A study of the distribution of Topoisomerase II alpha (Topo II) in cel ls of six tissue culture cell lines, human (HeLa), mouse (L929), rat, Indian muntjac, rat kangaroo (PTK-2), and wallaby revealed the followi ng features: (1) There is a cell cycle association of a specific popul ation of Topo II with the centromere, (2) The centromere is distinguis hed from the remainder of the chromosome by the intensity of its Topo II reactivity. (3) The first appearance of a detectable population of Topo II at the centromere varies between species but is correlated wit h the onset of centromeric heterochromatin condensation, (4) Detectabl e centromeric Topo II declines at the completion of cell division. (5) The distribution pattern of Topo II within the centromere is species- and stage-specific and is conserved only within the kinetochore domai n. In addition, we report that the Topo II inhibitor ICRF-193 can prev ent the normal accumulation of Topo II at the centromere, This results in the disruption of chromatin condensation sub-adjacent to the kinet ochore as well as the perturbation of kinetochore structure. Taken tog ether, our studies indicate that the distribution of Topo II at the ce ntromere is unlike that reported for the remainder of the chromosome a nd is essential for proper formation of centromere/kinetochore structu re.