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RNA-dependent DNA polymerase activity in intracytoplasmic type-a particles of mouse mammary tumors

V Wunderlich, S Zotter, G Sydow

    Acta Biologica Et Medica Germanica
    |January 1, 1976
    PubMed

    Insights

    Purified type-A particles from mouse mammary tumors show RNA-dependent DNA polymerase activity. This enzyme functions both intrinsically and when stimulated by templates, preferring magnesium ions.

    Area of Science:

    • Virology
    • Molecular Biology
    • Oncology

    Background:

    • Mouse mammary tumors are associated with specific viral particles.
    • Intracytoplasmic type-A particles (IAP) are found within these tumor cells.
    • The enzymatic properties of IAPs are not fully characterized.

    Purpose of the Study:

    • To investigate the enzymatic activity of purified intracytoplasmic type-A particles.
    • To determine if these particles possess RNA-dependent DNA polymerase activity.
    • To characterize the cofactor preferences of the identified enzyme.

    Main Methods:

    • Isolation and purification of intracytoplasmic type-A particles from mouse mammary tumors using gradient centrifugation.
    • Assay of endogenous RNA-dependent DNA polymerase activity.
    • Assay of exogenous (template-stimulated) RNA-dependent DNA polymerase activity.
    • Enzyme activity assays with varying divalent cation concentrations, focusing on magnesium ions.

    Main Results:

    • Purified intracytoplasmic type-A particles demonstrated RNA-dependent DNA polymerase activity.
    • The enzyme exhibited both endogenous and template-stimulated polymerase functions.
    • A clear preference for magnesium ions (Mg2+) as a cofactor was observed.

    Conclusions:

    • Intracytoplasmic type-A particles harbor an RNA-dependent DNA polymerase.
    • This enzyme activity can be both intrinsic and template-driven.
    • Magnesium ions are crucial for the optimal function of this viral enzyme.

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