Investigation of the mechanism of higher order chromatin fragmentation observed in drug-induced apoptosis

H. M. Beere, C. M. Chresta, A. Alejo-Herberg, A. Skladanowski, C. Dive, A. K. Larsen, J. A. Hickman

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Apoptosis is characterized by the nonrandom cleavage of DNA. After continuous treatment of MOLT-4 human T lymphoblastoid cells with the topoisomerase II inhibitor etoposide (50 μM) and the nongenotoxic agent N- methylformamide (300 mM), apoptosis was confirmed by electron microscopy. Analysis of DNA integrity by conventional gel electrophoresis failed to detect internucleosomal DNA cleavage. Resolution of DNA by field inversion gel electrophoresis showed fragments of 50 kilobases (kb). Etoposide induced the transient appearance of an additional DNA band of >600 kb, which was temporally coincident with DNA-protein complex formation and was rapidly reversible upon drug removal. This DNA band was not observed after N- methylformamide treatment. In situ DNA end-labeling showed the incorporation of biotinylated dUTP into 50-kb DNA fragments but not etoposide-induced DNA fragments of >600 kb. DNA end-labeling with terminal deoxynucleotidyltransferase was therefore not dependent upon internucleosomal DNA cleavage, and fragments of approximately 50 kb were characterized by free 3'-OH termini that were not occluded by topoisomerase II protein. Although we considered that topoisomerase II potentially played an active role in the fragmentation of higher order chromatin during apoptosis, the results showed that DNA cleavage by topoisomerase II induced reversible, protein-associated fragments of >600 kb and not irreversible cleavage to 50-kb fragments. The reversible cleavage of DNA to fragments of >600 kb appears to be a signal for the engagement of apoptosis and is not an initial step in the sequential unwinding of chromatin.
    Original languageEnglish
    Pages (from-to)986-996
    Number of pages10
    JournalMolecular pharmacology
    Volume47
    Issue number5
    Publication statusPublished - 1995

    Keywords

    • Apoptosis/drug effects/*physiology
    • Cell Line
    • Chromatin/drug effects/*metabolism/ultrastructure
    • DNA/drug effects/metabolism
    • DNA Damage
    • Etoposide/pharmacology
    • Formamides/pharmacology
    • Humans
    • Microscopy, Electron
    • T-Lymphocytes/drug effects/metabolism/ultrastructure
    • Topoisomerase II Inhibitors

    Fingerprint

    Dive into the research topics of 'Investigation of the mechanism of higher order chromatin fragmentation observed in drug-induced apoptosis'. Together they form a unique fingerprint.

    Cite this