These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Incomplete reversion of double stranded DNA cleavage mediated by Drosophila topoisomerase II: formation of single stranded DNA cleavage complex in the presence of an anti-tumor drug VM26.
    Author: Lee MP, Hsieh T.
    Journal: Nucleic Acids Res; 1992 Oct 11; 20(19):5027-33. PubMed ID: 1329036.
    Abstract:
    Anti-tumor drug VM26 greatly stimulates topoisomerase II mediated DNA cleavage by stabilizing the cleavable complex. Addition of a strong detergent such as SDS to the cleavable complex induces the double stranded DNA cleavage. We demonstrate here that heat treatment can reverse the double stranded DNA cleavage; however, topoisomerase II remains bound to DNA even in the presence of SDS. This reversed complex has been shown to contain single strand DNA breaks with topoisomerase II covalently linked to the nicked DNA. Chelation of Mg++ by EDTA and the addition of salt to a high concentration also reverse the double strand DNA cleavage, and like heat reversion, topoisomerase II remains bound to DNA through single strand DNA break. The reversion complex can be analyzed and isolated by CsCl density gradient centrifugation. We have detected multiple discrete bands from such a gradient, corresponding to protein/DNA complexes with 1, 2, 3, ..... topoisomerase II molecules bound per DNA molecule. Analysis of topoisomerase II/DNA complexes isolated from the CsCl gradient indicates that there are single stranded DNA breaks associated with the CsCl stable complexes. Therefore, topoisomerase II/DNA complex formed in the presence of VM26 cannot be completely reversed to yield free DNA and enzyme. We discuss the possible significance of this finding to the mechanism of action of VM26 in the topoisomerase II reactions.
    [Abstract] [Full Text] [Related] [New Search]