Identification of the functional regulatory region of the neurotrophin-3 gene promoter.

The 5'-flanking region of the human neurotrophin-3 (NT-3) gene was isolated from a human placental genomic library using the oligonucleotide corresponding to the 5'-noncoding region of the NT-3 cDNA as a probe. A 3.8 kbp genomic fragment containing the 5'-flanking region, the first exon and a portion of the first intron was isolated and sequenced. The transcriptional initiation site, identified by S1 nuclease mapping, was located 27 bp downstream from the TATA-like sequence. Several plasmids, in which the NT-3 promoter regions were fused to the chloramphenicol acetyltransferase (CAT) gene, were constructed. Transient expression in human glioma Hs683 cells demonstrated that a fragment of about 0.1 kbp from the transcriptional initiation site was sufficient for promoter activity. While, in human plasma cell leukemia ARH77 cells, in which NT-3 mRNA was not detected, the region upstream from -65 functioned to silence CAT activity. It is suggested that this region contains the transcriptional regulatory element for the specific expression of the NT-3 gene.