The human c-fps/fes gene product expressed ectopically in rat fibroblasts is nontransforming and has restrained protein-tyrosine kinase activity.
A 13-kilobase EcoRI genomic restriction fragment containing the human c-fps/fes proto-oncogene locus was expressed transiently in Cos-1 monkey cells and stably in Rat-2 fibroblasts. In both cases, human c-fps/fes directed synthesis of a 92-kilodalton protein-tyrosine kinase (p92c-fes) indistinguishable from a tyrosine kinase previously identified with anti-fps antiserum which is specifically expressed in human myeloid cells. Transfected Rat-2 cells containing approximately 50-fold more human p92c-fes than is found in human leukemic cells remained morphologically normal and failed to grow in soft agar. Synthesis of p92c-fes in this phenotypically normal line exceeded that of the P130gag-fps oncoprotein in a v-fps-transformed Rat-2 line. Despite this elevated expression, human p92c-fes induced no substantial increase in cellular phosphotyrosine and was not itself phosphorylated on tyrosine. In contrast, p92c-fes immunoprecipitated from these Rat-2 cells or expressed as an enzymatically active fragment in Escherichia coli from a c-fps/fes cDNA catalyzed tyrosine phosphorylation with an activity similar to that of v-fps/fes polypeptides. Thus, p92c-fes is not transforming when ectopically overexpressed in Rat-2 fibroblasts. This lack of transforming activity correlates with a restriction imposed on the kinase activity of the normal c-fps/fes product in vivo which is apparently lifted for v-fps/fes oncoproteins, suggesting that regulatory interactions within the host cell modify fps/fes protein function and normally restrain its oncogenic potential.
Greer
P A
PA
Department of Molecular and Developmental Biology, Mount Sinai Hospital Research Institute, Toronto, Ontario, Canada.
Meckling-Hansen
K
K
Pawson
T
T
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002460:Cell Line; D005347:Fibroblasts / Q000201:enzymology; D005796:Genes; D006801:Humans; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000032:analysis; D010957:Plasmids; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D000090063:Proto-Oncogene Mas; D011519:Proto-Oncogenes; D051381:Rats; D014158:Transcription, Genetic; D014162:Transfection; D014357:Trypsin
D000596:Amino Acids; C000715470:MAS1 protein, human; D010748:Phosphopeptides; D000090063:Proto-Oncogene Mas; D011505:Protein-Tyrosine Kinases; D014357:Trypsin