[Isolation of mutant genes for human leukocyte alpha2-interferon by a method of localized mutagenesis].

An efficient method to obtain the mutant genes for human leucocyte alpha 2-interferon (IFN) has been elaborated. The technique includes the following main stages: cloning of interferon gene in M13mp8 DNA; isolation of double-stranded hybrid DNA complex, containing IFN gene as a single-stranded fragment; selective modification of a single-stranded hybrid DNA by sodium bisulphite; the repair of hybrid DNA by DNA polymerase I from Escherichia coli, transformation of Escherichia coli JN103 cells by double-stranded circular DNA, containing the selectively modified gene IFN. The technique is based on the protection of bacteriophage M13 genome from mutagen induced damage by means of converting phage DNA into the double-stranded structure leaving the single-stranded fragment to be mutagenized prone to mutagen action. This is achieved by reannealing of single-stranded M13mpB DNA hydrolyzed by restriction endonuclease BamHI. The technique preserves the infectiousness of vector DNA under the conditions permitting modification of up to 10% cytosine residues in IFN gene. Every clone resulting from transformation of Escherichia coli by modified DNA carried mutations in IFN gene, identified by sequencing after Sanger.