Cloning and Expression of a Novel Variant of Human Interferon-γ cDNA

Abstract

A cDNA library was prepared from the poly(A) mRNA isolated from human peripheral blood lymphocytes which were induced by combined treatment with phytohemagglutinin and a phorbol ester. Recombinant plasmids containing human interferon-γ (HuIFN-γ) cDNAs were identified by the oligonucleotide-hybridization method. Nucleotide sequence analysis showed that the nucleotide and amino-acid sequences of HuIFN-γ cDNA in plasmid pIFNγ-G4 differed from the published data at amino acid position 9 (CAA for glutamine versus AAA for lysine). The cDNA in plasmid pIFNγ-G4 was expressed under control of the simian virus 40 early promoter in monkey COS cells and a biologically active HuIFN-γ was secreted from the cells. The cDNA was also inserted into an expression vector carrying an E. coli tryptophan promoter and was expressed in E. coli. The results suggest that the conversion from lysine to glutamine at amino acid position 9 might not affect the specific activity of HuIFN-γ.