[IL-3 gene, receptor and signal transduction]

Interleukin 3 (IL-3) plays a critical role in growth and differentiation of myeloid cells. The human IL-3 gene, located on chromosome 5 contains several cis-acting DNA sequences, i.e. CLE (conserved lymphokine element) and a GC rich region, similar to the GM-CSF gene. The expression of the GM-CSF and IL-3 genes in activated T cells may be regulated coordinately through these cis-regulatory elements. Recently, reconstitution experiments using isolated cDNA clones for receptor subunits have revealed that two distinct proteins are required for the high affinity receptors for GM-CSF, IL-3 and IL-5; the alpha subunits bind with the corresponding ligands with low affinity, and the beta subunit is shared in common. Tyrosine kinase activity appears to be involved in the signal transduction of the IL-3 and GM-CSF receptors.