CHARACTERIZATION OF A PROMOTER WITHIN THE FIRST INTRON OF THE HUMAN CD4 GENE

The CD4 molecule is subject to complex regulation during T cell differ entiation and activation. The elements regulating CD4 gene expression have only partially been defined. In this report, we identified a prom oter element located in the first intron of the CD4 gene. This promote r preferentially functions in T cell lines and is preferentially activ e in CD4+, CD8+ cells. These findings are similar to other systems in which multiple promoters define tissue- and developmental-specific pat terns of expression. Through a series of deletions, electrophoretic mo bility shift assays and exonuclease III protection assays, we localize d the basal promoter element to a 32-bp fragment. This element lacks p otential binding domains for myb and ets, both of which have previousl y been shown to be involved in the function of the 5' murine and human CD4 promoter, and this suggests the presence of a novel, T-cell-speci fic transcription factor. These results also suggest that the CD4 expr ession requires the use of multiple regulatory elements located throug hout the CD4 gene.