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Phosphorylation of a 36,000 Mr cellular protein in cells infected with partial transformation mutants of rous sarcoma

K D Nakamura, M J Weber

    Molecular and Cellular Biology
    |February 1, 1982
    PubMed

    Insights

    Mutant Rous sarcoma viruses reveal that tyrosine phosphorylation of a 36,000 Mr protein is not essential for all cancer-like cell changes. However, this phosphorylation may be required for malignant growth properties.

    Area of Science:

    • Virology
    • Molecular Biology
    • Oncology

    Background:

    • Rous sarcoma virus (RSV) causes cell transformation through its pp60src protein.
    • Understanding the specific roles of pp60src targets is crucial for cancer research.

    Purpose of the Study:

    • To investigate the role of tyrosine phosphorylation of a 36,000 Mr protein in Rous sarcoma virus-induced cell transformation.
    • To correlate this specific phosphorylation event with various transformation parameters.

    Main Methods:

    • Isolation and characterization of Rous sarcoma virus mutants with altered pp60src activity.
    • Analysis of pp60src-mediated tyrosine phosphorylation of a 36,000 Mr protein in infected cells.
    • Correlation of phosphorylation levels with specific transformation phenotypes.

    Main Results:

    • Phosphorylation of the 36,000 Mr protein was not necessary or sufficient for loss of fibronectin, loss of density-dependent growth inhibition, morphological changes, increased hexose transport, or loss of cell adhesion.
    • The strongest correlation observed was with increased plasminogen activator levels.
    • Mutant CU2, with low 36,000 Mr protein phosphorylation, showed deficiencies in anchorage-independent growth and tumorigenicity.

    Conclusions:

    • Tyrosine phosphorylation of the 36,000 Mr protein is not a universal requirement for all RSV-induced transformation parameters.
    • This specific phosphorylation event may be essential for the acquisition of malignant growth properties, such as anchorage-independent growth and tumorigenicity.

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