Structure of the chromosomal gene for murine interleukin 3.

We have isolated the mouse interleukin 3 (IL-3) gene from a mouse sperm DNA library based on homology with the mouse mast-cell growth-factor (MCGF) cDNA sequence. The nucleotide sequence determined for the gene and its flanking regions reveals that the IL-3 gene is composed of four introns and five exons. The nucleotide sequence of the exons agrees with that determined for the MCGF cDNA. A "TATA"-like sequence preceded by a G + C-rich region is found in the 5' flanking region. At the 3' region of the second intron are nine repeats of a closely related 14-base-pair (bp) sequence. These repeated sequences share extensive homology with a 20-bp repeated sequence found in the human genome, which was shown to have enhancer activity. Eight out of nine repeats form a 73-bp duplicated sequence and each 73-bp repeat contains sequences homologous to the core sequence suggested for enhancer elements. These sequences may play a role in the expression of the IL-3 gene in concanavalin A- or antigen-stimulated T lymphocytes. Stable transformants of L cells generated by co-transformation of the IL-3 gene with pSV2neo constitutively express MCGF activity indicating that the isolated gene is functional in vivo.