Mitotic chromatin condensation in vitro using somatic cell extracts and nuclei with variable levels of endogenous topoisomerase II.
We report the development of a new method for producing mitotic extracts from tissue culture cells. These extracts reproducibly promote the condensation of chromatin in vitro when incubated with purified interphase nuclei. This condensation reaction is not species specific, since nuclei from chicken, human, and hamster cell lines all undergo chromatin condensation upon incubation with the extract. We have used this extract to investigate the role of DNA topoisomerase II (topo II) in the chromosome condensation process. Chromatin condensation does not require the presence of soluble topo II in the mitotic extract. However, the extent of formation of discrete chromosome-like structures correlates with the level of endogenous topo II present in the interphase nuclei. Our results further suggest that chromatin condensation in this extract may involve two processes: chromatin compaction and resolution into discrete chromosomes.
Wood
E R
ER
Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Earnshaw
W C
WC
D000818:Animals; D002467:Cell Nucleus / Q000502:physiology; D002474:Cell-Free System; D002642:Chick Embryo; D002843:Chromatin / Q000502:physiology*; D002875:Chromosomes / Q000502:physiology*; D004250:DNA Topoisomerases, Type II / Q000502:physiology*; D004330:Drosophila; D004912:Erythrocytes / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D007399:Interphase; D008938:Mitosis / Q000502:physiology*; D009685:Nuclear Envelope / Q000378:metabolism
D002843:Chromatin; D004250:DNA Topoisomerases, Type II