Mutations within the 5' half of the avian retrovirus MC29 v-myc gene alter or abolish transformation of chicken embryo fibroblasts and macrophages.
Avian myelocytomatosis virus MC29 induces a wide variety of neoplastic diseases in infected birds and transforms cells of the macrophage lineage as well as fibroblasts and epithelial cells. A biological and biochemical analysis, carried out on a series of in-frame insertion and deletion mutations within the gag-myc gene of MC29, revealed several mutations within the 5' portion of the v-myc gene that encode proteins either completely defective for transformation or compromised in their ability to transform chicken embryo fibroblasts but not macrophages. Mutations within the 3' end of the v-myc gene which disrupt sequences encoding the basic/helix-loop-helix region were defective for transformation of both fibroblasts and macrophages. Eight variants were cloned into the replication-competent avian expression vector RCAS. Analysis of cells infected with transformation-defective, replication-competent viruses confirmed the expression of functionally defective Myc proteins. Further, expression of the transformation defective variant dl91-137 in chicken fibroblasts inhibited subsequent transformation by wild-type MC29. The results reported herein support the hypothesis that Myc proteins function as regulators of transcription in a variety of cell types and clearly point out the necessity of putative regulatory domains within the amino-terminal half of the Myc protein.
Farina
S F
SF
Department of Microbiology and Cancer Center, University of Virginia Health Sciences Center, Charlottesville 22908.
Huff
J L
JL
Parsons
J T
JT
D000818:Animals; D001354:Avian Leukosis Virus / Q000235:genetics* / Q000472:pathogenicity; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D002642:Chick Embryo; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D005347:Fibroblasts / Q000382:microbiology; D015681:Fusion Proteins, gag-onc / Q000235:genetics; D016259:Genes, myc / Q000235:genetics*; D014644:Genetic Variation; D005822:Genetic Vectors; D008264:Macrophages / Q000382:microbiology; D009154:Mutation; D016274:Oncogene Protein p55(v-myc) / Q000096:biosynthesis / Q000235:genetics*; D010641:Phenotype; D014158:Transcription, Genetic; D014162:Transfection
D015681:Fusion Proteins, gag-onc; D016274:Oncogene Protein p55(v-myc)