NUCLEAR FACTOR-IL6 ACTIVATES THE HUMAN IL-4 PROMOTER IN T-CELLS

Positive regulatory element I (PRE-I) is a strong enhancer element ess ential for expression of the human IL-4 gene. To identify transcriptio n factors binding to PRE-I, we screened a cDNA expression library from Jurkat T cells and isolated a cDNA encoding nuclear factor (NF)-IL6 ( also known as C/EBP beta). NF-IL6 mRNA was found in human Jurkat T cel ls and in the mouse Th2 clone D10, but not in Th1 clone 29. rNF-IL6 ex pressed in bacteria wa's shown to specifically bind to PRE-I. PRE-I fo rms multiple DNA-protein complexes with nuclear extracts from jurkat c ells. Some of these complexes were demonstrated to contain NF-IL6 by u sing anti-C/EBP beta Abs. Overexpression of NF-IL6 enhanced expression of the chloramphenicol acetyl transferase reporter gene linked to the PRE-I-thymidine kinase or the human IL-4 promoter more than 10-fold i n Jurkat cells. Promoter deletion studies revealed two additional NF-I L6 binding sites located at positions -44 to -36 (C/EBP proximal) and -87 to -79 (C/EBP medial), respectively. Our results demonstrate that NF-IL6 is involved in transcriptional activation of the human IL-4 pro moter in T cells.