CLONING OF THE CDNA-ENCODING HUMAN C/EBP-GAMMA, A PROTEIN-BINDING TO THE PRE-I ENHANCER ELEMENT OF THE HUMAN INTERLEUKIN-4 PROMOTER

The positive regulatory element-I (PRE-I) is a strong enhancer element essential for expression of the human interleukin-4 (IL-4)-encoding gene, In order to identify transcription factors binding to PRE-I, we screened a cDNA expression library from human Jurkat T-cells. A cDNA encoding the human CCAAT/enhancer binding protein-gamma (hC/EBP gamma) was cloned. The deduced amino acid (aa) sequence of hC/EBP gamma contains 150 aa with high homology to mouse Ig/EBP-1 and rat C/EBP gamma. The mRNA of hC/EBP gamma is expressed at a high level in Jurkat T-cells in three forms generated via differential polyadenylation. DNA-binding experiments with recombinant protein produced in bacteria demonstrate that hC/EBP gamma binds to PRE-I, but not to unrelated DNA fragments. Our data also show that hC/EBP gamma may cooperate with Fos to bind to PRE-I.