Transcriptional regulation of human cytosolic phospholipase A2α gene

• Main Authors: Wei-Chiao Wang, 王薇喬
• Other Authors: Wen-Chang Chang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/78260697697440520161

碩士 === 國立成功大學 === 藥理學研究所 === 92 === 　　cPLA2α ( cytosolic phospholipase A2 α) is the major intracellular form ofPLA2, which selectively hydrolyzes membrane phospholipids at the sn-2　position, and the rate-limiting enzyme in the eicosanoid production. In thepresent study, we found that phorbol 12-myristate 13-acetate ( PMA ), anactivator of PKC, and proinflammatory cytokine, IL-1β, increased the expression of cPLA2α mRNA and protein synthesis in a time-dependent manner in A549 cells. But the molecular mechanism was seems different. Reporter assays revealed the PMA response element was in the region of —53 to -35 bp. Furthermore, the promoter activity of cPLA2α gene induced by c-Jun activation was also regulated in the same manner as PMA. By using the DNA affinity precipitation assay in A549 cells, Sp1 directly interacted with the atypical Sp1 site of the promoter and the binding pattern between Sp1 and DNA was not changed between the control and PMA treated cells. However, PMA increased the binding of c-Jun to Sp1. Because there is no typical AP1 binding sequence in this promoter region, Sp1 may act as a carrier protein to bring c-Jun to the promoter to transactivate the transcriptional activity of cPLA2α gene. In the gene regulation of cPLA2α by IL-1β, it failed to induce the promoter activity of cPLA2α gene. But we found that IL-1β increased the half-life of cPLA2α mRNA, indicating a role for post-transcriptional modulation of gene expression. The AU-rich region of the 3’-UTR of cPLA2αis highly conserved across species. Insertion of the entire 3’-UTR of cPLA2α into the 3’-UTR of luciferase resulted in a 80﹪decrease in luciferase activity and IL-1β somewhat recovered the decrease in luciferase activity. In this study, we delineated the contributions of transcriptional and post-transcriptional process to the regulation of cPLA2α gene expression in response to a variety of agonists in A549 cells.