title: Abelson murine leukaemia virus transformation involves loss of epidermal growth factor-binding sites.
abstract: Malignant transformation by mammalian RNA sarcoma viruses has previously been shown to involve a reduction in receptor sites for a well characterized 6,000-molecular weight (MW) growth-promoting substance, designated epidermal growth factor (EGF). Although Abelson murine leukaemia virus (AbLV) resembles sarcoma viruses in its ability to transform embryo fibroblasts in cell culture, AbLV induces a rapid B-cell lymphoid leukaemia rather than fibrosarcomas in vivo. The major translational product of AbLV is a highly phosphorylated polyprotein of MW 120,000 which exhibits an associated tyrosine-specific protein kinase activity and probable transforming function. We show here that AbLV transformation resembles transformation by RNA sarcoma viruses with respect to the abolition of EGF-binding sites. EGF binding is restored to control levels following loss of polyprotein expression in morphological revertants of AbLV-transformed clones and remains uninfluenced in cell lines infected with transformation-defective (td) AbLV mutants encoding polyproteins deficient in protein kinase activity. These findings indicate that AbLV transformation involves a polyprotein-associated, tyrosine-specific protein kinase activity which mediates its effect through a mechanism resulting directly or indirectly in the abolition of EGF-binding sites.
mesh_terms: D000011:Abelson murine leukemia virus; D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D002472:Cell Transformation, Viral; D004815:Epidermal Growth Factor / Q000378:metabolism*; D009052:Leukemia Virus, Murine; D008907:Mink; D010455:Peptides / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D010455:Peptides; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D014443:Tyrosine; D004815:Epidermal Growth Factor; D011494:Protein Kinases