Studies of the 5'Region of the Cytosolic Phospholipase A2 Gene

Shelhamer, J

Abstract

Phospholipase A2s are families of enzymes that catalyze the hydrolysis of the sn-2 ester bond of phospholipids. Cytosolic phospholipase A2 (cPLA2) is a high molecular weight PLA2 which preferentially hydrolyzes phospholipids containing arachidonic acid in the sn-2 position. In some cells, cPLA2 activity and protein levels may be regulated by cytokines and growth factors. Therefore, it was of interest to investigate further the regulation of gene expression of this enzyme by characterizing the 5' promoter region of the cPLA2 gene. A probe consisting of the 5' portion of the known cDNA sequence of cPLA2 was used to screen a genomic library in Lambda phage. A clone was isolated from the library that contained a 20 kB insert. After Eco R1 digestion of the insert, a 5.7 kB fragment that bound the probe was subcloned into a Bluescript phage and sequenced. The transcription initiation site was identified by primer extension and by rapid amplification of 5' cDNA ends. DNA sequence analysis of the 595 base pairs 5' to the transcription initiation site revealed a 48 base pair purine-pyrimidine dinucleotide repeat, five interferon gamma response elements, and one interferon gamma activated sequence. The promoter does not have a TATA box. The promoter appears to contain an initiator element. The 595 base pair sequence has promoter activity in a luciferase reporter gene system. Current work involves the construction of reporter genes with approximately 1 and 2kB inserts in order to further study the properties of the 5' region of the cPLA2 gene. Studies of the initiator element are also under way. An understanding of the induction mechanisms of gene expression of this enzyme may allow for novel approaches to control eicosanoid production in inflammatory diseases of the airways.