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Analysis of DNA Double-strand Break (DSB) Repair in Mammalian Cells
13:10

Analysis of DNA Double-strand Break (DSB) Repair in Mammalian Cells

Published on: September 8, 2010

Enzymatic restriction of mammalian cell DNA: evidence for double-strand breaks as potentially lethal lesions

P E Bryant

    International Journal of Radiation Biology and Related Studies in Physics, Chemistry, and Medicine
    |July 1, 1985
    PubMed

    Insights

    Restriction enzymes Pvu II and Bam H1 were used to create DNA double-strand breaks (dsb) in hamster cells. Pvu II, creating blunt-ended dsb, mimicked X-ray cell death, suggesting blunt-ended breaks are lethal and clastogenic.

    Area of Science:

    • Molecular Biology
    • Cell Biology
    • Genetics

    Background:

    • Mammalian cell death after X-ray exposure is hypothesized to result from DNA double-strand breaks (dsb) and subsequent chromosomal aberrations.
    • Previous studies indicated Pvu II induces chromosome aberrations, while Bam H1 does not.

    Purpose of the Study:

    • To test the hypothesis that X-ray-induced mammalian cell death stems from DNA dsb and chromosomal aberrations.
    • To investigate the lethal and clastogenic potential of blunt-ended versus cohesive-ended DNA breaks.

    Main Methods:

    • Permeabilized Chinese hamster cells were treated with restriction endonucleases Pvu II (blunt ends) and Bam H1 (cohesive ends).
    • Cellular clonogenic ability was assayed to determine cell survival.
    • Chromosomal aberrations were previously assessed for these enzymes.

    Main Results:

    • Pvu II treatment caused a dose-dependent loss of reproductive integrity in mammalian cells, simulating X-ray exposure effects.
    • Blunt-ended DNA double-strand breaks induced by Pvu II were found to be both potentially clastogenic and lethal.
    • Bam H1, generating cohesive-ended breaks, did not significantly reduce cell survival within the tested enzyme dose range.

    Conclusions:

    • DNA double-strand breaks with blunt ends are potentially clastogenic and lethal to mammalian cells.
    • These findings support the model where X-ray-induced cell death involves DNA dsb leading to lethal chromosomal aberrations.
    • Aberrations may cause lethality through genetic material loss or chromosome bridge formation.

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