Breakage of single-stranded DNA by eukaryotic type 1 topoisomerase occurs only at regions with the potential for base-pairing.

Journal Article

Eukaryotic type 1 DNA topoisomerases break single-stranded DNA at specific sites. A preferred site for rat liver topoisomerase breakage in single-stranded phi X174 DNA was located within a region of the DNA with the potential for duplex formation. To investigate the relationship between sites of breakage in duplex and single-stranded DNA, a restriction fragment containing sequences from the transcriptional regulatory and enhancer region of the simian virus 40 genome was used as a substrate for topoisomerase. While different patterns of breakage in the native and denatured forms of the DNA were observed, some sites of breakage were common to both forms. The break sites in the denatured DNA were a subset of the break sites in the duplex DNA and were located in regions which had the potential for intrastrand base-pairing due to distal complementary sequences. A series of single-stranded fragments were generated with the distal complementary sequences deleted and these fragments were used as substrates for topoisomerase breakage. The lack of detectable breakage at a site when the complementary sequence was deleted, suggests that topoisomerase acts at duplex regions in the single-stranded DNA and that it is not active on regions of single-stranded DNA that are not base-paired.

Full Text

Duke Authors

Cited Authors

  • Been, MD; Champoux, JJ

Published Date

  • December 15, 1984

Published In

Volume / Issue

  • 180 / 3

Start / End Page

  • 515 - 531

PubMed ID

  • 6098684

International Standard Serial Number (ISSN)

  • 0022-2836

Language

  • eng

Conference Location

  • England