CLONING AND PROMOTER ANALYSIS OF THE HUMAN B-50 GAP-43 GENE/

We here report isolation of exon 1 and analysis of the human B-50 prom oter. A human genomic lambda EMBL3 library was screened with a homolog ous PCR probe. Two independent clones were analyzed and partially sequ enced: They contained up to 5 kb sequence upstream of the translation start site and approx 13 kb of intron 1 sequence. There was a high deg ree of homology between the rat and the human gene with 100% homology from -504 to -427, with respect to the translation start codon. Howeve r, relatively long GT and GA repeats as seen in the rat gene were abse nt. Various promoter-reporter constructs, containing 5.0 to 0.12 kb of the upstream region, were transfected into undifferentiated and neuro ectodermally differentiated P19-EC. Two promoter activities were found . The minimal fragment with promoter activity still responsive to diff erentiation was the 0.22 kb construct, similar to rat promoter P2. We conclude that the human B-50 gene is expressed in a similar way to the rat B-50 gene, based on the presence of two transcripts, the high deg ree of homology between the rat and the human sequence, and the two pr omoter activities found in P19-EC cells.