Functional Studies on the Promoter Region of the Human GTP Cyclohydrolase I Gene

We have isolated genomic clones that contained the gene for human GTP cyclohydrolase I. One clone containing the 5'-regulatory region of this gene was further analysed. It encompassed the first exon, parts of the first intron and about 2.6kb of the promoter region. The transcription start site was localised by rapid amplification of cDNA ends (5'-RACE). The 2.6 kb region upstream of the transcription start site showed promoter activity when ligated upstream of a reporter gene. 5'-truncations of the promoter region increased its activity as long as the CAAT and TATA boxes remained unchanged. Several putative Spl responsive elements were located within a GC-rich region close to the transcription start site