DNA topoisomerases are enzymes that control and modify the topological states of DNA. This proposal aims at the elucidation of their biological roles and the molecular mechanisms by which they act. The methods of contemporary molecular biology will be applied. The possible involvement of the two known eukaryotic DNA topoisomerases in a number of processes, including gene expression, nucleosome assembly, chromosomal translocation, excision of integrated viral sequences, and replication, will be tested. Topoisomerase mutants will also be used to determine whether intracellular DNA in eukaryotic organisms is actively maintained in the underwound or negatively supercoiled state by the topoisomerases. Genetic and biochemical approaches will also be used to test whether the cellular target of a number of antitumor drugs is eukaryotic DNA topoisomerase II, and whether a protein kinase activity tightly associated with this enzyme is an intrinsic activity of the enzyme. Drug-resistant mutants of eukaryotic DNA topoisomerase II will be obtained to determine how these drugs enhance DNA cleavage by the topoisomerase. Studies of the roles of the two ATP-independent topoisomerases in bacterium, topoisomerase I and III, will be continued. Extensive mechanistic studies of both eukaryotic and prokaryotic DNA topoisomerases will be continued by the use of chemical, biochemical, and genetic analyses.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Molecular Biology Study Section (MBY)
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Harvard University
Schools of Arts and Sciences
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Kwan, Kelvin Y; Greenwald, Rebecca J; Mohanty, Subhasis et al. (2007) Development of autoimmunity in mice lacking DNA topoisomerase 3beta. Proc Natl Acad Sci U S A 104:9242-7
Azarova, Anna M; Lyu, Yi Lisa; Lin, Chao-Po et al. (2007) Roles of DNA topoisomerase II isozymes in chemotherapy and secondary malignancies. Proc Natl Acad Sci U S A 104:11014-9
Lyu, Yi Lisa; Lin, Chao-Po; Azarova, Anna M et al. (2006) Role of topoisomerase IIbeta in the expression of developmentally regulated genes. Mol Cell Biol 26:7929-41
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Jiang, Xiaofeng (2005) Random mutagenesis of the B'A' core domain of yeast DNA topoisomerase II and large-scale screens of mutants resistant to the anticancer drug etoposide. Biochem Biophys Res Commun 327:597-603
Stupina, Vera A; Wang, James C (2004) DNA axial rotation and the merge of oppositely supercoiled DNA domains in Escherichia coli: effects of DNA bends. Proc Natl Acad Sci U S A 101:8608-13
Lyu, Yi Lisa; Wang, James C (2003) Aberrant lamination in the cerebral cortex of mouse embryos lacking DNA topoisomerase IIbeta. Proc Natl Acad Sci U S A 100:7123-8
Kwan, Kelvin Y; Moens, Peter B; Wang, James C (2003) Infertility and aneuploidy in mice lacking a type IA DNA topoisomerase III beta. Proc Natl Acad Sci U S A 100:2526-31
Wang, Yong; Lynch, A Simon; Chen, Sue-Jane et al. (2002) On the molecular basis of the thermal sensitivity of an Escherichia coli topA mutant. J Biol Chem 277:1203-9
Wang, Yong; Lyu, Yi Lisa; Wang, James C (2002) Dual localization of human DNA topoisomerase IIIalpha to mitochondria and nucleus. Proc Natl Acad Sci U S A 99:12114-9

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