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  • Title: Different topoisomerase II antitumor drugs direct similar specific long-range fragmentation of an amplified c-MYC gene locus in living cells and in high-salt-extracted nuclei.
    Author: Gromova II, Thomsen B, Razin SV.
    Journal: Proc Natl Acad Sci U S A; 1995 Jan 03; 92(1):102-6. PubMed ID: 7816796.
    Abstract:
    We have analyzed the long-range distribution of topoisomerase II-mediated cleavages induced in an amplified human c-MYC gene locus in the presence of several antitumor agents. The long-range cleavage patterns were found to be nonrandom and similar for all antitumor drugs tested. Cleavages occurred within several kilobase-long areas (approximately 5 kb) highly accessible to topoisomerase II and separated by extended regions (approximately 70-100 kb) of less accessibility, possibly reflecting the mode of DNA organization into loops along the chromosome. Within the cleavage areas, the patterns of cleavage sites showed a certain dependence on the type of drug used for entrapment of topoisomerase II-DNA complexes. Importantly, distribution of cleavage areas in native chromatin and histone-depleted nuclei was very similar, if not identical, suggesting that the primary target of antitumor agents in vivo is topoisomerase II associated with the high-salt-insoluble nuclear matrix. These data show that matrix-attached DNA is preferentially damaged by topoisomerase II-targeting agents, which may be an important cellular event contributing to drug-induced cell death.
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