Detection of Human Leukocyte Interferon-αA and -α2Genes in Genomic DNAs by the Use of Deoxyoctadecyloligonucleotide Probes

Abstract

Two deoxyoctadecyloligonucleotides complementary to the sequence spanning a single base substitution between human leukocyte interferon (HuIFN) αA and α₂ genes were efficiently used as probes to distinguish between HuIFN-αA and -α₂ genes. At 37°C or 42°C under aqueous conditions (0.9 M NaCI), hybridization between both probes and the αA and α₂ genes without any mismatch was strong, whereas the hybridization with one base mismatch (αA probe-α₂ gene and α₂ probe-αA gene) was very weak or negligible. Because the single base substitution of G in the α₂ gene for A in the αA gene provides an extra HinfI site in the α₂ gene at the center of the sequence hybridizing to the α₂ probe, digestion with HinfI restriction endonuclease caused complete loss of the hybridization between the α₂ probe and the α2 gene. PvuII digestion provides 298-bp fragments hybridizing to the probes only from the αA and α₂ genes among the known HuIFN-α genes. Thus, with the use of these oligonucleotide probes in combination with PvuII and PvuII-HinfI restriction endonuclease digestion, the existence of the sequences corresponding to both IFN-αA and IFN-α₂ genes in human genomic DNAs was demonstrated. The results also surprisingly indicate that these genes, formerly considered alleles because of their essential identity (1 base pair difference in the coding sequence), are not likely to be alleles, but represent closely related distinct genes.