Intranuclear distribution of DNA topoisomerase II and chromatin.

Domain-specific anti-Drosophila DNA topoisomerase II antibodies were generated, affinity purified and used for confocal laser scanning immunofluorescence microscopy. Except for the nucleolus, DNA topoisomerase II is distributed throughout interphase nuclei. In adult accessory glands as well as third instar larval neural ganglion and imaginal disk nuclei, DNA topoisomerase II shows areas of co-localization with chromatin adjacent to areas of extrachromosomal distribution. These observations made in a variety of tissues under different fixation conditions and with a number of molecular probes support the notion that DNA topoisomerase II is a component of a substantially extrachromosomal network that functions to organize interphase chromatin within nuclei.