Dynamic association of topoisomerase II to the mitotic chromosomes in live cells of Aspergillus nidulans.
DNA topoisomerase II (Topo II) is an essential enzyme that catalyzes topological changes of DNA and consists of a major member of mitotic chromosomes. To investigate the dynamic localization of Topo II in nuclei, we engineered the strain of Aspergillus nidulans expressing Topo II fused with green fluorescent protein (GFP). Time-lapse microscopy revealed that the distribution of Topo II-GFP in nuclei varied depending on the cell cycle. In interphase, Topo II-GFP distributed evenly in the nucleoplasm and at the onset of G2 phase became concentrated into nucleolus. During mitosis, Topo II-GFP accumulated on chromosomes, when the chromosomes condensed. In the early mitosis, the Topo II also showed a single or two brighter spots among the fluorescence of clumped chromosomes. The spots once divided into several spots and then concentrated again into a spot per nucleus in the dividing nuclei of anaphase. Along with the subsequent decondensation of chromosomes, Topo II diffused back into nucleoplasm.
Kawagishi
Mika
M
Division of Molecular Mycology and Medicine, Center for Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Akashi
Tomohiro
T
Kikuchi
Akihiko
A
D001233:Aspergillus nidulans / Q000166:cytology / Q000235:genetics* / Q000378:metabolism*; D002467:Cell Nucleus; D015825:Chromosomes, Fungal / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D007700:Kinetics; D008938:Mitosis / Q000502:physiology*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D011993:Recombinant Fusion Proteins; D004250:DNA Topoisomerases, Type II