In transient transfection experiments, a construct encoding the entire regulatory region of the GR gene, including eight of the alternate exon 1 sequences and the splice acceptor site within the intron 5' of exon 2, was fused to a lucif erase reporter gene. The lucif erase gene is activated by the coupled promoters and its activity thus reflects the ability of the regulatory sites to activate gene transcription - hence the term reporter gene. Fusion to the socalled reporter gene permits a measure of the degree to which individual sequences can potentially influence gene expression. This alteration in activity results from various sequences originating at any point within the regulatory region and, we presume, represents the sum of the activity of individual promoters on the genomic DNA fragment. In subsequent studies examining the potency of the individual promoters, we found that the relative activity of the individual exon 1 sequences is similar, with one notable exception, the exon 17 promoter sequence. The fused exon 17 has the highest transcriptional activity of any single promoter construct. More recent studies confirm the
