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Phosphorylation of the nonstructural proteins encoded by three avian acute leukemia viruses and by avian fujinami

K Bister, W H Lee, P H Duesberg

    Journal of Virology
    |November 1, 1980
    PubMed

    Insights

    Nonstructural gag proteins from avian acute leukemia and Fujinami sarcoma viruses are phosphoproteins. These viral proteins exhibit higher phosphorylation than helper viral proteins, with some possessing associated kinase activity.

    Area of Science:

    • Molecular Biology
    • Virology
    • Oncogenesis

    Background:

    • Avian acute leukemia viruses (MC29, CMII) and Fujinami sarcoma virus (FSV) possess gag gene-related nonstructural proteins.
    • Understanding the post-translational modifications of these viral proteins is crucial for comprehending viral replication and oncogenic potential.

    Purpose of the Study:

    • To investigate the phosphorylation status of nonstructural gag proteins from avian acute leukemia and Fujinami sarcoma viruses.
    • To determine if these viral proteins possess associated kinase activity.

    Main Methods:

    • Immunoprecipitation of viral proteins from cellular lysates using anti-gag serum.
    • In vivo and in vitro phosphorylation assays using 32P labeling.
    • Enzyme activity assays to assess kinase function.

    Main Results:

    • Nonstructural gag proteins from MC29, CMII, and FSV were identified as phosphoproteins in vivo.
    • These viral phosphoproteins showed significantly higher 32P radioactivity compared to intracellular helper viral gag proteins.
    • The 140,000-dalton FSV and 110,000-dalton MC29 proteins were phosphorylated in vitro by associated kinase activity.
    • This kinase activity was separable or inactivated under specific conditions (normal serum treatment, ultracentrifugation).

    Conclusions:

    • Nonstructural gag proteins of avian acute leukemia and Fujinami sarcoma viruses are phosphorylated in vivo.
    • Associated kinase activity phosphorylates these viral proteins in vitro, suggesting a potential regulatory role.
    • Further research is needed to ascertain if these viral proteins possess intrinsic kinase activity.

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