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Updated: May 12, 2026

Aip1p Dynamics Are Altered by the R256H Mutation in Actin
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Published on: July 30, 2014

Mutagenesis of Fujinami sarcoma virus: evidence that tyrosine phosphorylation of P130gag-fps modulates its biological

G Weinmaster, M J Zoller, M Smith

    Cell
    |June 1, 1984
    PubMed

    Insights

    Tyrosine phosphorylation enhances the activity of Fujinami sarcoma virus (FSV) P130gag-fps protein kinase. Mutating a key tyrosine site reduced transformation but retained kinase ability, showing phosphorylation

    Area of Science:

    • Oncology
    • Virology
    • Molecular Biology

    Background:

    • Fujinami sarcoma virus (FSV) encodes a 130 kd transforming protein (P130gag-fps) with tyrosine-specific protein kinase activity.
    • This protein is phosphorylated at tyrosine and serine residues in transformed cells, suggesting a regulatory role.

    Purpose of the Study:

    • To investigate the role of tyrosine phosphorylation in the function of FSV P130gag-fps.
    • To determine if specific phosphorylation sites modulate the protein's kinase and transforming activities.

    Main Methods:

    • Oligonucleotide-directed mutagenesis was used to alter the major tyrosine phosphorylation site (Y1073) in the FSV genome to phenylalanine.
    • The transforming ability and in vitro kinase activity of the mutant FSV and its P130gag-fps protein were compared to wild-type FSV.

    Main Results:

    • Mutant FSV induced cell transformation with a significantly longer latent period compared to wild-type FSV.
    • The P130gag-fps protein from the mutant retained tyrosine kinase activity but showed a five-fold reduction in activity in vitro.
    • Tyrosine phosphorylation was identified as a key modulator of both biochemical and biological functions of FSV P130gag-fps.

    Conclusions:

    • Tyrosine phosphorylation is essential for the optimal biochemical and biological activities of FSV P130gag-fps.
    • This study establishes a precedent for amino acid modification modulating protein function in viral transformation.

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