Is DNA topoisomerase II beta a nucleolar protein?

We have carried out immunofluorescence labelling of two human cell types, Hela cells and peripheral blood lymphocytes, prepared by several different fixation/permeabilization protocols using a variety of antibodies against DNA Topoisomerase II (Topo II). We have found that the distribution of Topo II alpha was overall similar during interphase and mitosis to that previously reported, regardless of antibody and of sample preparation. On the other hand, the interphase distribution of Topo II beta was quite variable, depending both on the antibody and on the method used to prepare the sample. Our interpretation of the data is that, like Topo II alpha, Topo II beta is primarily a nucleoplasmic protein, but that unlike Topo II alpha, small amounts are also associated with intranucleolar chromatin. (C) 1996, Wiley-Liss, Inc.