An SP1‐like 5′‐GACCACGCC‐3′ sequence is critical for activity of the inflammatory phospholipase A₂ promoter and binds several non‐zinc finger proteins

Abstract

We have previously shown that the promoter of the type IIa secreted phospholipase A2 gene contains a strong positive regulatory proximal element [-125 to -85] element B. Mutation of this element abolishes the activation of the phospholipase A2 promoter by C/EBPbeta in HepG2 cells. Liver nuclear proteins form three major and two minor complexes with this element. The [-107 to -99] 5'-GACCACGCC-3' sequence is critical for the formation of these complexes and the activity of the promoter. Although the sequence of element B is highly similar to those of Sp1 binding sites, it does not bind Sp1 or other zinc-finger proteins. Each major complex contains a single protein, the molecular masses of these proteins being 100, 90 and 75 kDa. These proteins have the same nucleotide requirements for binding, with the cytosines at positions -102, -100, -99 and the adenosine at -103 being the most important nucleotides. The activity of the phospholipase A2 promoter in HeLa cells was lower than in HepG2 cells, and was correlated with the absence of complex 3 in HeLa cell nuclear extracts. Our results suggest different roles for the proteins bound to the 5'-GACCACGCC-3' sequence. In particular, the 75-kDa protein which forms the third complex is critical for the activity of the promoter of the secretory phospholipase A2 gene.