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Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase
07:27

Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase

Published on: April 29, 2010

Characterization of an RNA-directed DNA polymerase found in association with murine intracytoplasmic A-particles

M Kohno, H Tanaka

    Journal of Virology
    |May 1, 1977
    PubMed

    Insights

    Researchers discovered an RNA-directed DNA polymerase in mouse leukemia A-particles. This enzyme uses the A-particle RNA as a template to synthesize DNA, a key finding in retrovirology research.

    Area of Science:

    • Molecular Biology
    • Virology
    • Biochemistry

    Background:

    • Intracytoplasmic A-particles are found in DBA/2 mouse leukemia cells.
    • The presence and function of associated enzymes within these particles were previously unclear.

    Purpose of the Study:

    • To identify and characterize enzymes associated with intracytoplasmic A-particles.
    • To determine the template used by any identified DNA polymerase.

    Main Methods:

    • Purification of intracytoplasmic A-particles from mouse leukemia cells.
    • Disruption of particles and assay for enzyme activity in the presence of deoxyribonucleoside triphosphates and divalent cations.
    • Cesium sulfate isopycnic gradient centrifugation to analyze synthesized DNA.
    • Hybridization studies between synthesized DNA and A-particle RNA.

    Main Results:

    • An RNA-directed DNA polymerase activity was detected in disrupted A-particles.
    • Enzyme activity required divalent cations (Mg2+ preferred over Mn2+) and all four deoxyribonucleoside triphosphates.
    • Synthesized DNA formed a DNA-RNA hybrid and hybridized with A-particle RNA.

    Conclusions:

    • The identified enzyme is an RNA-directed DNA polymerase.
    • Endogenous A-particle RNA serves as the template for this DNA polymerase.
    • This suggests a potential role for reverse transcription in the replication or function of these particles.

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