title: Inhibition of topoisomerase II by 8-chloro-adenosine triphosphate induces DNA double-stranded breaks in 8-chloro-adenosine-exposed human myelocytic leukemia K562 cells.
abstract: 8-Chloro-cAMP and 8-chloro-adenosine (8-Cl-Ado) are known to inhibit proliferation of cancer cells by converting 8-Cl-Ado into an ATP analog, 8-chloro-ATP (8-Cl-ATP). Because type II topoisomerases (Topo II) are ATP-dependent, we infer that 8-Cl-Ado exposure might interfere with Topo II activities and DNA metabolism in cells. We found that 8-Cl-Ado exposure inhibited Topo II-catalytic activities in K562 cells, as revealed by decreased relaxation of the supercoiled pUC19 DNA and inhibited decatenation of the kinetoplast DNA (kDNA). In vitro assays showed that 8-Cl-ATP, but not 8-Cl-Ado, could directly inhibit Topo IIalpha-catalyzed relaxation and decatenation of substrate DNA. Furthermore, 8-Cl-ATP inhibited Topo II-catalyzed ATP hydrolysis and increased salt-stabilized closed clamp. In addition, 8-Cl-Ado exposure decreased bromo-deoxyuridine (BrdU) incorporation into DNA and led to enhanced DNA double-stranded breaks (DSBs) and to increased formation of gamma-H2AX nuclear foci in exposed K562 cells. Together, 8-Cl-Ado/8-Cl-ATP can inhibit Topo II activities in cells, thereby inhibiting DNA synthesis and inducing DNA DSBs, which may contribute to 8-Cl-Ado-inhibited proliferation of cancers.
authors.affiliation: Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Xue Yuan Road 38, Beijing 100083, PR China.
authors.forename: Sheng-Yong
authors.initials: SY
authors.lastname: Yang
authors.forename: Xiu-Zhen
authors.initials: XZ
authors.lastname: Jia
authors.forename: Li-Yan
authors.initials: LY
authors.lastname: Feng
authors.forename: Shu-Yan
authors.initials: SY
authors.lastname: Li
authors.forename: Guo-Shun
authors.initials: GS
authors.lastname: An
authors.forename: Ju-Hua
authors.initials: JH
authors.lastname: Ni
authors.forename: Hong-Ti
authors.initials: HT
authors.lastname: Jia
mesh_terms: D015762:2-Chloroadenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D055162:Biocatalysis; D004249:DNA Damage; D006801:Humans; D006868:Hydrolysis; D020014:K562 Cells; D007951:Leukemia, Myeloid / Q000473:pathology*; D059005:Topoisomerase II Inhibitors
chemical_list: D059005:Topoisomerase II Inhibitors; D015762:2-Chloroadenosine; D000255:Adenosine Triphosphate; C075440:8-chloroadenosine