Characterization of a promoter within the first intron of the human CD4 gene

The CD4 molecule is subject to complex regulation during T cell differentiation and activation. The elements regulating CD4 gene expression have only partially been defined. In this report, we identified a promoter element located in the first intron of the CD4 gene. This promoter preferentially functions in T cell lines and is preferentially active in CD4+, CD8+ cells. These findings are similar to other systems in which multiple promoters define tissue- and developmental-specific patterns of expression. Through a series of deletions, electrophoretic mobility shift assays and exonuclease III protection assays, we localized the basal promoter element to a 32-bp fragment. This element lacks potential binding domains for myb and ets, both of which have previously 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-specific transcription factor. These results also suggest that the CD4 expression requires the use of multiple regulatory elements located throughout the CD4 gene.