Molecular Characterization of Bovine Prostaglandin G/H Synthase-2 and Regulation in Uterine Stromal Cells

Prostaglandin G/H synthase (PGHS) is a key rate-limiting enzyme in the prostaglandin biosynthetic pathway, and prostaglandins play a central role in the control of the reproductive cycle. The objectives of this study were to clone and characterize the primary structure of bovine PGHS-2 and to study its regulation in uterine stromal cells in vitro. The bovine PGHS-2 cDNA was cloned by a combination of reverse transcription-polymerase chain reaction and cDNA library screening. Results showed that the complete bovine PGHS-2 cDNA is composed of a 5′-untranslated region of 128 bp, an open reading frame of 1815 bp, and a 3′-untranslated region of 1565 bp containing multiple repeats (n = 11) of the Shaw-Kamen sequence 5′-ATTTA-3′. The open reading frame encodes a 604-amino acid protein that is 86–97% identical to other mammalian PGHS-2 homologs. The regulation of PGHS-2 mRNA and protein was studied in primary cultures of bovine uterine stromal cells stimulated with phorbol 12-myristate 13-acetate (PMA; 100 nM). Northern and Western blot analyses reveal a marked induction in PGHS-2 transcript (4.0 kilobases) and protein ( M r = 72 000) after 3–12 h of PMA stimulation ( P < 0.05). However, this induction was transient in nature as levels of PGHS-2 mRNA and protein returned to basal levels after 24 h of PMA stimulation. In contrast, PMA had no effect on levels of PGHS-1 ( P > 0.05). The PMA-dependent induction of PGHS-2 was associated with a significant increase in prostaglandin E 2 secretion in the culture media ( P < 0.05). To study promoter activity of the 5′-flanking DNA region of the bovine PGHS-2 gene, the genomic fragment −1574/−2 (+1 = transcription start site), as well as a series of 5′-deletion mutants, were fused upstream of the firefly luciferase gene and transiently transfected into primary cultures of bovine uterine stromal cells. Results showed that a first promoter region located between −1574 and −492 and a second region between −88 and −39 appear to play important roles in PMA-dependent regulation of PGHS-2 promoter activity in bovine uterine cells. Thus, this study characterizes for the first time the structure of the bovine PGHS-2 transcript and the deduced amino acid sequence of its encoded protein and establishes an in vitro model to study the regulation of PGHS-2 gene expression in bovine uterine tissue.