Structure of the mitogen-inducible TIS10 gene and demonstration that the TIS10-encoded protein is a functional prostaglandin G/H synthase.

The TIS10 cDNA was cloned as a primary response gene transcript whose mRNA rapidly accumulates in 3T3 cells treated with serum, polypeptide growth factors, or phorbol esters. The sequence of the TIS10 cDNA suggested that the gene encodes a protein with strong similarities to prostaglandin G/H synthase/cyclooxygenase (EC 1.14.99.1). Transient transfection into COS-1 cells of an expression vector driving the TIS10 cDNA leads to production and secretion of prostaglandin E2. Microsomes prepared from COS-1 cells transfected with this construct demonstrate both hydroperoxidase and cyclooxygenase activities similar to that demonstrated by cells transfected with a vector encoding the ovine prostaglandin G/H synthase. These data demonstrate that the TIS10 gene encodes a functional prostaglandin synthase/cyclooxygenase distinct from the prostaglandin synthase/cyclooxygenase whose cDNAs and/or genes have previously been cloned from sheep, mouse, and man. The structure of the TIS10 gene, determined by a combination of sequencing of genomic clones and polymerase chain reactions from genomic clones, demonstrates remarkable exon-intron conservation with the human prostaglandin synthase/cyclooxygenase gene. A 1-kilobase sequence located immediately proximal to the start site of transcription of the TIS10 gene can confer phorbol ester and serum inducibility to a luciferase reporter gene following transient transfection into NIH 3T3 cells, suggesting that this region of the gene is responsible for transcriptional regulation of the TIS10 gene by mitogens in fibroblasts.