Prostaglandin A1 enhances c-fos expression and activating protein-1 activity

Abstract Prostaglandin A 1 (PGA 1 ) increases heat shock element (HSE)-mediated transcription, thereby enhancing expression of HSE-bearing genes, including heat shock proteins. Because we recently found functional HSEs in the human and rodent c - fos promoters, we hypothesized that PGA 1 might increase c - fos expression through the HSE. In this study, we revealed that PGA 1 induces c - fos expression at least partly by increasing the binding between heat shock factor-1 and the HSE, and that PGA 1 enhances activity of activating protein-1 (AP-1). Interestingly, so far as PGA 1 is present in the medium, AP-1-mediated transcription enhanced by PGA 1 cannot be detected by the standard luciferase reporter gene assay. Instead, it can be detected by either checking luciferase mRNA levels in the presence of PGA 1 or measuring luciferase activities just after removal of PGA 1 . These results showed that protein products of some stress-responsive genes can increase, not during the stressful condition, but immediately after recovery from stress.