High-level expression of oncogenes in Escherichia coli.

A plasmid, pJL6, was constructed that contains a unique Cla I site 12 codons beyond the bacteriophage lambda cII gene initiation codon, as well as an adjacent unique Hind III site. These sites allowed us to fuse the sequences from the avian myelocytomatosis virus (MC29) v-myc gene, the avian myeloblastosis virus (AMV) v-myb gene, and the Harvey murine sarcoma virus (Ha-MuSV) v-ras gene to the amino-terminal portion of the cII gene. Transcription of the hybrid genes is controlled from the lambda PL promoter. When this promoter is derepressed, E. coli cells harboring the chimeric plasmid produce levels of fusion proteins that amount to over 5% of total cellular protein. Antibodies raised by the cII-myc fusion protein form an immunoprecipitate with the MC29 gene product, P110gag-myc. The cII-ras fusion protein is precipitated by monoclonal antibodies directed toward the Ha-MSV p21ras, binds GDP, and is capable of autophosphorylation.