Topoisomerase IIalpha maintains genomic stability through decatenation G(2) checkpoint signaling.
Topoisomerase IIalpha (topoIIalpha) is an essential mammalian enzyme that topologically modifies DNA and is required for chromosome segregation during mitosis. Previous research suggests that inhibition of topoII decatenatory activity triggers a G(2) checkpoint response, which delays mitotic entry because of insufficient decatenation of daughter chromatids. Here we examine the effects of both topoIIalpha and topoIIbeta on decatenatory activity in cell extracts, DNA damage and decatenation G(2) checkpoint function, and the frequencies of p16(INK4A) allele loss and gain. In diploid human fibroblast lines, depletion of topoIIalpha by small-interfering RNA was associated with severely reduced decatenatory activity, delayed progression from G(2) into mitosis and insensitivity to G(2) arrest induced by the topoII catalytic inhibitor ICRF-193. Furthermore, interphase nuclei of topoIIalpha-depleted cells showed increased frequencies of losses and gains of the tumor suppressor genetic locus p16(INK4A). This study shows that the topoIIalpha protein is required for decatenation G(2) checkpoint function, and inactivation of decatenation and the decatenation G(2) checkpoint leads to abnormal chromosome segregation and genomic instability.
Bower
J J
JJ
Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
Karaca
G F
GF
Zhou
Y
Y
Simpson
D A
DA
Cordeiro-Stone
M
M
Kaufmann
W K
WK
D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002842:Chromatids / Q000235:genetics; D020090:Chromosome Segregation / Q000502:physiology; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054659:Diketopiperazines; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D016195:G2 Phase / Q000187:drug effects / Q000235:genetics*; D019942:Genes, p16; D042822:Genomic Instability; D006801:Humans; D008938:Mitosis / Q000187:drug effects / Q000235:genetics; D010879:Piperazines / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics; D059005:Topoisomerase II Inhibitors
D000951:Antigens, Neoplasm; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D054659:Diketopiperazines; D010879:Piperazines; D059005:Topoisomerase II Inhibitors; C070899:4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione; D004247:DNA; D004250:DNA Topoisomerases, Type II