STRUCTURE OF THE HUMAN CYCLO-OXYGENASE-2 GENE

Cyclo-oxygenase (Cox), a rate-limiting enzyme in the synthesis of pros tanoids, is encoded by two genes, Cox-1 and Cox-2, which are different ially expressed and regulated. Human Cox-1 and -2 polypeptides share 6 1% primary sequence identity. While the expression of Cox-1 is maximal in quiescent cells, Cox-2 expression is induced by growth factors and cytokines, We have screened a human genomic library with a probe from the 5'-untranslated region (UTR) of the human Cox-2 (hCox-2) cDNA and isolated two overlapping genomic clones. We have determined the DNA s equence of 0.8 kb upstream of the transcription start site, 6 kb of pr otein coding region, which includes 10 exons and 9 introns, as well as 2.5 kb of the 3'-UTR. The structures of the hCox-1 and hCox-2 and the murine TIS10 (Cox-2) genes are highly conserved, with a few exception s. The 3'-UTRs of the Cox-1 and -2. genes are distinct; for example, t he largest exon in the Cox-2 gene encodes the entire 3'-UTR, containin g 22 copies of the AUUUA' RNA instability element. Sequence analysis o f the 5'-flanking region has shown several potential transcription reg ulatory sequences, including a TATA box, a C/EBP motif, two AP-2 sites , three SP1 sites, two NF-kappa B sites, a CRE motif and an Ets-1 site . These efforts serve as a basis for future studies on transcriptional and post-transcriptional mechanisms of Cox-2 gene regulation.