Abstract: Amplified expression of recombinant DNA products is achieved in hosts expressing protease that cleave at multi-basic amino acid residues. To this end, wild-type genes encoding the desired protein products are mutated by substituting codons or eliminating codons encoding multi-basic amino acid residues while maintaining the activity of the expressed protein product. Mutation of the desired gene can be conveniently carried out by site-specific in vitro mutagenisis.

Abstract: A process for preparing bovine interleukin-2 (bIL-2) by culturing a microbial host transformed by a vector containing a DNA sequence encoding bIL-2 under conditions suitable for the expression of bIL-2 and recovering bIL-2.

Abstract: A chemically-synthesized oligonucleotide composing a portion of the nucleotide sequence of the human IL-2 is employed as a probe to isolate the gene coding for human IL-2. The human IL-2 gene is selected from a cDNA library prepared from RNA produced by mitogen-stimulated Jurkat cells. Double-stranded cDNA is prepared from polyadenylated RNA extracted from bovine cells thought to produce interleukin-2. Such cDNA is inserted within a plasmid vector and the recombinant plasmid employed to transform hosts. Plasmid DNA, prepared from pools of the transformed hosts, is hybridized with a probe composed of a large portion of the coding sequence of the human IL-2 gene. Pools of host cells that provide signal to the human cDNA probe are identified, subdivided, and rescreened until a single positive colony is identified. Bovine plasmid cDNA is prepared from this colony, and the bIL-2 gene is sequenced.