Molecular cloning and structure of the mouse interleukin-5 gene

We isolated the chromosomal gene for mouse interleukin-5 (IL-5) from genomic libraries using a cloned mouse IL-5 cDNA as probe. Nucleotide sequence determination of the IL-5 gene and its flanking regions showed that the gene was composed of four exons. The sequence homologies of the exons 1, 2, 3, and 4 of the human and murine IL-5 genes are 70, 79, 85, and 77%, respectively. TATA-like and CAAT-like sequences were found 25 and 52 base-pairs, respectively, upstream of the transcription initiation site which was identified by S1 mapping analysis. The nucleotide sequences of the mouse and human IL-5 genes were about 70% homologous in the 5'-flanking region extending to 200 base-pairs upstream of the transcription initiation site, beyond which the homology declined rapidly. The sequence surrounding 50 base-pairs upstream of the initiation site was conserved among genes for other lymphokines: such as mouse granulocyte/macrophage colony stimulating factor, mouse IL-2, and mouse IL-4.