Synthesis in E. coli of a polypeptide with human leukocyte interferon activity

Double-stranded cDNA prepared from the 12S fraction of poly(A) RNA from interferon (IF)-producing human leukocytes was cloned in Escherichia coli using the pBR322 vector. One of the resulting clones had a 910-base pair insert which could hybridise to IF mRNA and was responsible for the production of a polypeptide with biological IF activity. Up to 10,000 units IF activity per g of cells was obtained from some clones.