Cloning and nucleotide sequence of the murine interleukin-3 gene

Southern hybridization analysis using a probe derived from a murine interleukin-3 (IL-3) cDNA clone revealed the presence of a single IL-3 gene in the haploid murine genome. An 8600-base-pair (8.6-kb) murine genomic EcoRI fragment containing the IL-3 gene was isolated by screening a library of size-fractionated genomic EcoRI fragments cloned in lambda gtWES X lambda B. The nucleotide sequence of a 3.5-kb region of the cloned DNA encompassing the IL-3 gene was determined. The gene contains four introns of 96, 993, 135 and 122 base pairs (bp), located within the coding region. The large intron contains 12 copies of a 14-15-bp tandem repeating sequence which resembles a human cellular homologue of a BKV enhancer sequence. The nucleotide sequence of the exons agrees exactly with that of an IL-3 cDNA cloned from WEHI-3, a tumorigenic cell line which over-produces IL-3, establishing that the unprocessed primary structure of IL-3 is identical in WEHI-3 and in BALB/c mice. Southern hybridization has revealed genomic alteration in the vicinity of the IL-3 gene in WEHI-3 cells.