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Position-specific effects of base mismatch on mammalian topoisomerase II DNA cleaving activity

Lookup NU author(s): Professor Caroline Austin, Dr Elaine Willmore

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Abstract

To further define the nucleic acid determinants of DNA site recognition by mammalian topoisomerase II, base mismatch effects on the enzyme DNA cleavage activity were determined in a 36-bp synthetic oligonucleotide corresponding to SV40 DNA. DNA cleavage sites induced by topoisomerase II without or with the antitumor drugs teniposide, idarubicin, or amsacrine were mapped using sequencing gels. Selected mismatches were studied, and always one of the two strands had the wild-type sequence. The effects of base mismatches were independent from the studied drugs. Mismatches introduced at the -4, -3, -2, or -1 positions, relative to the enzyme cleavage site, often abolished, or much reduced. DNA cleavage, whereas those at +1 and +2 positions often increased DNA breakage or were without influence. Mismatches at more distant positions, e.g., -7, -8, etc., had no effect. Those at positions -5 and -6 sometimes increased cleavage levels. These effects were always observed at sites already cleaved in the wild-type oligomer: new sites of cleavage were not induced by the studied mismatches. These results were obtained both for the native murine topoisomerase II and for the two recombinant human isozymes. No difference between topoisomerases II α(p170) and β(p180) was seen in their response to mismatches. The results demonstrate that topoisomerase II recognition of the DNA site of cleavage requires fully paired nucleotides at the 3' terminus. Nevertheless, similarly to other DNA strand transferase enzymes, both topoisomerase II isoforms may have a sequence-specific nicking activity at the 5' side of unpaired bases.


Publication metadata

Author(s): Bigioni, M., Zunino, F., Tinelli, S., Austin, C. A., Willmore, E., Capranico, G.

Publication type: Article

Publication status: Published

Journal: Biochemistry

Year: 1996

Volume: 35

Issue: 1

Pages: 153-159

Print publication date: 09/01/1996

ISSN (print): 0006-2960

ISSN (electronic): 1943-295X

URL: http://dx.doi.org/10.1021/bi951736p

DOI: 10.1021/bi951736p

PubMed id: 8555169


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