Molecular characterization of the 5.2 KB isoform of the human cyclooxygenase-1 transcript

Several cDNA clones from human endothelial cells were isolated by expression cloning with the polyclonal antisera against the Ram seminal vesicle cyclooxygenase enzyme (Cox-1). One such clone produced a fusion protein that reacted with two other Cox-1 antiserum (Hla, T., Farrell, M.P., Kumar, A. and Bailey, J.M. (1986) Prostaglandins 32 (6) 829-845). The 2.5 kb cDNA insert was sequenced and contained 60 bp encoding the C-terminal end of the human Cox-1 polypeptide, followed by 2.3 kb of untranslated region. Northern blot analysis of human endothelial cells using the 2.5 kb cDNA insert detected the 2.8 and 5.2 kb Cox-1 transcripts. These data indicated that the isolated clone represented the 5.2 kb isoform of the human Cox-1 mRNA. The presence of the canonical polyadenylation site AAUAAA at 740 bp downstream from the translation termination codon suggests that alternative polyadenylation of the Cox-1 gene gives rise to 5.2 and 2.8 kb isoforms. The sequence of the 3'-UTR of the Cox-1 transcripts is highly divergent from that of the human Cox-2 transcript isoforms, suggesting a distinct function in the regulation of expression at the post-transcriptional and/or translational levels.