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DNA synthesis and repair in permeable cells of Micrococcus radiodurans

S Kitayama, A Matsuyama

    Biochimica Et Biophysica Acta
    |February 5, 1976
    PubMed

    Insights

    Micrococcus radiodurans permeable cells showed stimulated DNA synthesis and strand rejoining after gamma-ray irradiation. Nicotinamide adenine dinucleotide (NAD) inhibited DNA synthesis but was required for rejoining damaged DNA.

    Area of Science:

    • Microbiology
    • Molecular Biology
    • Radiation Biology

    Background:

    • Micrococcus radiodurans is known for its exceptional resistance to ionizing radiation.
    • Understanding DNA repair mechanisms in radioresistant bacteria is crucial for radiation biology and biotechnology.

    Purpose of the Study:

    • To investigate DNA synthesis and strand rejoining in Micrococcus radiodurans cells permeable to deoxyribonucleoside triphosphates.
    • To elucidate the role of nicotinamide adenine dinucleotide (NAD) in DNA repair processes following gamma-ray exposure.

    Main Methods:

    • Preparation of Micrococcus radiodurans cells permeable to deoxyribonucleoside triphosphates.
    • In vitro assays for DNA synthesis and DNA strand rejoining.
    • Exposure of cells to gamma-rays and assessment of DNA repair in the presence and absence of NAD.

    Main Results:

    • ATP stimulated DNA synthesis in permeable cells, requiring all four deoxyribonucleoside triphosphates and MgCl2.
    • Nicotinamide adenine dinucleotide (NAD) inhibited DNA synthesis but was essential for the rejoining of gamma-ray-induced DNA strand scissions.
    • Irradiation stimulated DNA synthesis, an effect abolished by NAD, while NAD enabled DNA rejoining in irradiated cells.

    Conclusions:

    • DNA synthesis and repair pathways in Micrococcus radiodurans are distinct and differentially regulated by NAD.
    • NAD plays a critical role in facilitating the rejoining of DNA strand breaks in irradiated Micrococcus radiodurans cells.

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