Alternative titles; symbols
HGNC Approved Gene Symbol: TOP2A
Cytogenetic location: 17q21.2 Genomic coordinates (GRCh38): 17:40,388,525-40,417,896 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 17q21.2 | DNA topoisomerase II, resistance to inhibition of, by amsacrine | 3 |
See 126420. DNA topoisomerases (EC 5.99.1.3) are enzymes that control and alter the topologic states of DNA in both prokaryotes and eukaryotes. Topoisomerase II from eukaryotic cells catalyzes the relaxation of supercoiled DNA molecules, catenation, decatenation, knotting, and unknotting of circular DNA. It appears likely that the reaction catalyzed by topoisomerase II involves the crossing-over of 2 DNA segments. Miller et al. (1981) estimated that there are about 100,000 molecules of topoisomerase II per HeLa cell nucleus, constituting about 0.1% of the nuclear extract. Since several of the abnormal characteristics of ataxia-telangiectasia (208900) appear to be due to defects in DNA processing, Singh et al. (1988) screened for these enzyme activities in 5 AT cell lines. In comparison to controls, the level of DNA topoisomerase II, determined by unknotting of P4 phage DNA, was reduced substantially in 4 of these cell lines and to a lesser extent in the fifth. DNA topoisomerase I, assayed by relaxation of supercoil DNA, was found to be present at normal levels.
Tsai-Pflugfelder et al. (1988) determined the entire coding sequence of the human TOP2 gene.
Chung et al. (1989) sequenced human cDNAs that had been isolated by screening a cDNA library derived from a mechlorethamine-resistant Burkitt lymphoma cell line (Raji-HN2) with a Drosophila Topo II cDNA. They identified 2 classes of sequence representing 2 TOP2 isoenzymes, which have been named TOP2A and TOP2B (126431). The sequence of 1 of the TOP2A cDNAs is identical to that of an internal fragment of the TOP2 cDNA isolated by Tsai-Pflugfelder et al. (1988). Southern blot analysis indicated that the TOP2A and TOP2B cDNAs are derived from distinct genes. Northern blot analysis using a TOP2A-specific probe detected a 6.5-kb transcript in the human cell line U937. Antibodies against a TOP2A peptide recognized a 170-kD protein in U937 cell lysates. Chung et al. (1989) concluded that their data provide genetic and immunochemical evidence for 2 TOP2 isozymes.
Lang et al. (1998) reported the complete structures of the TOP2A and TOP2B genes. The TOP2A gene spans approximately 30 kb and contains 35 exons.
Tsai-Pflugfelder et al. (1988) showed that the human topoisomerase II enzyme is encoded by a single-copy gene which they mapped to 17q21-q22 by a combination of in situ hybridization of a cloned fragment to metaphase chromosomes and by Southern hybridization analysis with a panel of mouse-human hybrid cell lines. Tan et al. (1992) confirmed the assignment to chromosome 17 by the study of somatic cell hybrids. Because of coamplification in an adenocarcinoma cell line, Keith et al. (1992) concluded that the TOP2A and ERBB2 (164870) genes may be closely linked on chromosome 17. Using probes that detected RFLPs at both the TOP2A and TOP2B loci, they demonstrated heterozygosity at a frequency of 0.17 and 0.37 for the alpha and beta loci, respectively. Kingsmore et al. (1993) mapped the mouse homolog to chromosome 11.
Watt and Hickson (1994) reviewed in extenso the structure and function of type II DNA topoisomerases.
Mondal and Parvin (2001) demonstrated that DNA topoisomerase II-alpha is associated with the pol II holoenzyme and is a required component of chromatin-dependent coactivation. Specific inhibitors of topoisomerase II blocked transcription on chromatin templates, but did not affect transcription on naked templates. Addition of purified topoisomerase II-alpha reconstituted chromatin-dependent activation activity in reactions with core pol II. Mondal and Parvin (2001) concluded that transcription on chromatin templates results in the accumulation of superhelical tension, making the relaxation activity of topoisomerase II essential for productive RNA synthesis on nucleosomal DNA.
Baxter et al. (2011) demonstrated that in yeast, centromeric plasmids undergo a dramatic change in their topology as the cells pass through mitosis. This change is characterized by positive supercoiling of the DNA and requires mitotic spindles and the condensin factor Smc2 (605576). When mitotic positive supercoiling occurs on decatenated DNA, it is rapidly relaxed by topoisomerase II. However, when positive supercoiling takes place in catenated plasmid, topoisomerase II activity is directed toward decatenation of the molecules before relaxation. Thus, a topologic change on DNA drives topoisomerase II to decatenate molecules during mitosis, potentially driving the full decatenation of the genome.
Chen et al. (2011) had found that expression of TOP2-alpha was inverse to expression of NFYB (189904), a subunit of a CCAAT-binding transcription factor. They found reduced TOP2-alpha and elevated NFYB expression in a CEM human lymphoblastic leukemia subline that was resistant to teniposide, a TOP2-alpha-targeting chemotherapeutic agent. MicroRNA profiling revealed reduced expression of MIR485-3p (615385) in teniposide-resistant cells. Overexpression of MIR485-3p downregulated NFYB via an MIR485-3p-binding site in the 3-prime UTR of the NFYB transcript, resulting in upregulated TOP2-alpha expression and restored sensitivity to teniposide. Overexpression of MIR485-3p also enhanced etoposide sensitivity in etoposide-resistant human rhabdomyosarcoma cells and in teniposide-resistant CEM cells. Chen et al. (2011) concluded that MIR485-3p-dependent downregulation of NFYB enhances cell sensitivity to TOP2-alpha inhibitors.
Dykhuizen et al. (2013) showed that BRG1 (603254)-associated factor (BAF) complexes decatenate newly replicated sister chromatids, a requirement for proper chromosome segregation during mitosis. Dykhuizen et al. (2013) found that deletion of Brg1 in mouse cells, as well as the expression of BRG1 point mutations identified in human tumors, leads to anaphase bridge formation (in which sister chromatids are linked by catenated strands of DNA) and a G2/M-phase block characteristic of the decatenation checkpoint. Endogenous BAF complexes interact directly with endogenous TOP2A through BAF250a (603024) and are required for the binding of TOP2A to approximately 12,000 sites across the genome. Dykhuizen et al. (2013) concluded that TOP2A chromatin binding is dependent on the ATPase activity of BRG1, which is compromised in oncogenic BRG1 mutants. They further concluded that the ability of TOP2A to prevent DNA entanglement at mitosis requires BAF complexes and suggested that this activity contributes to the role of BAF subunits as tumor suppressors.
Schellenberg et al. (2017) found that the SUMO ligase ZNF451 (615708) is a multifunctional DNA repair factor that controls cellular responses to genotoxic DNA-protein crosslinks that play a role in the regulation of DNA topology by TOP2 through the production of transient DNA double-strand breaks. ZNF451 binding to TOP2 cleavage complex (TOP2cc), a protein-DNA crosslink that is the key intermediate in the TOP2 reaction, facilitates a proteasome-independent tyrosyl-DNA phosphodiesterase-2 (TDP2; 605764) hydrolase activity on stalled TOP2cc. The ZNF451 SUMO ligase activity further promotes TDP2 interactions with SUMOylated TOP2, regulating efficient TDP2 recruitment through a 'split-SIM' SUMO2 engagement platform. Schellenberg et al. (2017) concluded that these findings uncovered a ZNF451-TDP2-catalyzed and SUMO2-modulated pathway for direct resolution of TOP2cc.
Crystal Structure
Dong and Berger (2007) presented the crystal structure at 3-angstrom resolution of a complex between the DNA-binding and cleavage core of S. cerevisiae topoisomerase-2 and a gate-DNA segment. The structure revealed that the enzyme enforces a 150-degree DNA bend through a mechanism similar to that of remodeling proteins such as integration host factor. Large protein conformational changes accompany DNA deformation, creating a bipartite catalytic site that positions the DNA backbone near a reactive tyrosine and a coordinated magnesium ion. This configuration closely resembles the catalytic site of type IA topoisomerases, reinforcing an evolutionary link between these structurally and functionally distinct enzymes. Binding of DNA facilitates opening of an enzyme dimerization interface, providing visual evidence for a key step in DNA transport.
In a human leukemia cell line, HL-60/AMSA, Hinds et al. (1991) found that resistance to inhibition of topoisomerase II by amsacrine and other intercalating agents was due to a single base change, AGA (arginine) to AAA (lysine); the single-base change was at nucleotide 1493 of the TOP2 gene, resulting in an arg486-to-lys (R486K) amino acid change.
Baxter, J., Sen, N., Lopez Martinez, V., Monturus De Carandini, M. E., Schvartzman, J. B., Diffley, J. F. X., Aragon, L. Positive supercoiling of mitotic DNA drives decatenation by topoisomerase II in eukaryotes. Science 331: 1328-1332, 2011. [PubMed: 21393545] [Full Text: https://doi.org/10.1126/science.1201538]
Chen, C.-F., He, X., Arslan, A. D., Mo, Y.-Y., Reinhold, W. C., Pommier, Y., Beck, W. T. Novel regulation of nuclear factor-YB by miR-485-3p affects the expression of DNA topoisomerase II-alpha and drug responsiveness. Molec. Pharm. 79: 735-741, 2011. [PubMed: 21252292] [Full Text: https://doi.org/10.1124/mol.110.069633]
Chung, T. D. Y., Drake, F. H., Tan, K. B., Per, S. R., Crooke, S. T., Mirabelli, C. K. Characterization and immunological identification of cDNA clones encoding two human DNA topoisomerase II isozymes. Proc. Nat. Acad. Sci. 86: 9431-9435, 1989. [PubMed: 2556712] [Full Text: https://doi.org/10.1073/pnas.86.23.9431]
Dong, K. C., Berger, J. M. Structural basis for gate-DNA recognition and bending by type IIA topoisomerases. Nature 450: 1201-1205, 2007. [PubMed: 18097402] [Full Text: https://doi.org/10.1038/nature06396]
Dykhuizen, E. C., Hargreaves, D. C., Miller, E. L., Cui, K., Korshunov, A., Kool, M., Pfister, S., Cho, Y.-J., Zhao, K., Crabtree, G. R. BAF complexes facilitate decatenation of DNA by topoisomerase II-alpha. Nature 497: 624-627, 2013. [PubMed: 23698369] [Full Text: https://doi.org/10.1038/nature12146]
Hinds, M., Deisseroth, K., Mayes, J., Altschuler, E., Jansen, R., Ledley, F. D., Zwelling, L. A. Identification of a point mutation in the topoisomerase II gene from a human leukemia cell line containing an amsacrine-resistant form of topoisomerase II. Cancer Res. 51: 4729-4731, 1991. [PubMed: 1651812]
Keith, W. N., Tan, K. B., Brown, R. Amplification of the topoisomerase II alpha gene in a non-small cell lung cancer cell line and characterisation of polymorphisms at the human topoisomerase II alpha and beta loci in normal tissue. Genes Chromosomes Cancer 4: 169-175, 1992. [PubMed: 1373318] [Full Text: https://doi.org/10.1002/gcc.2870040211]
Kingsmore, S. F., Tang, C.-M., Lo, C.-F., Hui, C.-K., Hwang, J., Seldin, M. F. Genetic mapping of the mouse topoisomerase II-alpha gene to chromosome 11. Mammalian Genome 4: 288-289, 1993. [PubMed: 8389625] [Full Text: https://doi.org/10.1007/BF00417440]
Lang, A. J., Mirski, S. E. L., Cummings, H. J., Yu, Q., Gerlach, J. H., Cole, S. P. C. Structural organization of the human TOP2A and TOP2B genes. Gene 221: 255-266, 1998. [PubMed: 9795238] [Full Text: https://doi.org/10.1016/s0378-1119(98)00468-5]
Miller, K. G., Liu, L. F., Englund, P. T. A homogeneous type II DNA topoisomerase from HeLa cell nuclei. J. Biol. Chem. 256: 9334-9339, 1981. [PubMed: 6267071]
Mondal, N., Parvin, J. D. DNA topoisomerase II-alpha is required for RNA polymerase II transcription on chromatin templates. Nature 413: 435-438, 2001. [PubMed: 11574892] [Full Text: https://doi.org/10.1038/35096590]
Schellenberg, M. J., Lieberman, J. A., Herrero-Ruiz, A., Butler, L. R., Williams, J. G., Munoz-Cabello, A. M., Mueller, G. A., London, R. E., Cortes-Ledesma, F., Williams, R. S. ZATT (ZNF451)-mediated resolution of topoisomerase 2 DNA-protein cross-links. Science 357: 1412-1416, 2017. [PubMed: 28912134] [Full Text: https://doi.org/10.1126/science.aam6468]
Singh, S. P., Mohamed, R., Salmond, C., Lavin, M. F. Reduced DNA topoisomerase II activity in ataxia-telangiectasia cells. Nucleic Acids Res. 16: 3919-3929, 1988. [PubMed: 2836804] [Full Text: https://doi.org/10.1093/nar/16.9.3919]
Tan, K. B., Dorman, T. E., Falls, K. M., Chung, T. D. Y., Mirabelli, C. K., Crooke, S. T., Mao, J. Topoisomerase II-alpha and topoisomerase II-beta genes: characterization and mapping to human chromosomes 17 and 3, respectively. Cancer Res. 52: 231-234, 1992. [PubMed: 1309226]
Tsai-Pflugfelder, M., Liu, L. F., Liu, A. A., Tewey, K. M., Whang-Peng, J., Knutsen, T., Huebner, K., Croce, C. M., Wang, J. C. Cloning and sequencing of cDNA encoding human DNA topoisomerase II and localization of the gene to chromosome region 17q21-22. Proc. Nat. Acad. Sci. 85: 7177-7181, 1988. [PubMed: 2845399] [Full Text: https://doi.org/10.1073/pnas.85.19.7177]
Watt, P. M., Hickson, I. D. Structure and function of type II DNA topoisomerases. Biochem. J. 303: 681-695, 1994. [PubMed: 7980433] [Full Text: https://doi.org/10.1042/bj3030681]