Functional compatibility between isoform alpha and beta of type II DNA topoisomerase.
DNA topoisomerase II (topo II) plays a crucial role in controlling the conformation of both DNA and whole chromosomes. This activity is essential for several cellular events such as DNA replication, transcription, chromosome condensation and segregation. In mammals, two genes code for isoforms of topo II, termed alpha and beta. They are similar in primary structure and have almost identical catalytic properties in vitro. We transfected HeLa cells with small interfering RNAs (siRNAs) targeted against either topo IIalpha or IIbeta, and succeeded in knocking down the expression of the corresponding protein. Chromosomes were condensed and aligned at metaphase in topo IIalpha-knockdown cells. Although some lagging chromosomes were observed, they were still segregated at anaphase despite the absence of topo IIalpha. When both topo IIalpha and topo IIbeta were removed, the segregation of chromosomes was severely arrested, suggesting that topo IIbeta could partially substitute for topo IIalpha. Double-knockdown experiments also revealed that topo II was required for shortening of the chromosome axis.
Laboratory of Medical Mycology, Research Institute for Disease Mechanism and Control, Nagoya University Graduate School and Faculty of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
Ayako
A
Sakaguchi
Akihiko
A
Kikuchi
D000951:Antigens, Neoplasm; D020090:Chromosome Segregation / Q000502:physiology; D002877:Chromosomes, Human / Q000201:enzymology; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D034741:RNA, Small Interfering / Q000235:genetics; D059005:Topoisomerase II Inhibitors; D014162:Transfection
D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; D059005:Topoisomerase II Inhibitors; D004250:DNA Topoisomerases, Type II