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

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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.