AN SP1-LIKE 5'-GACCACGCC-3' SEQUENCE IS CRITICAL FOR ACTIVITY OF THE INFLAMMATORY PHOSPHOLIPASE A(2) PROMOTER AND BINDS SEVERAL NON-ZINC FINGER PROTEINS

We have previously shown that the promoter of the type IIa secreted ph ospholipase A, gene contains a strong positive regulatory proximal ele ment [-125 to -85] element B. Mutation of this element abolishes the a ctivation of the phospholipase A(2) promoter by C/EBP beta in HepG2 ce lls. Liver nuclear proteins form three major and two minor complexes w ith this element. The [-107 to -99] 5'-GACCACGCC-3' sequence is critic al for the formation of these complexes and the activity of the promot er. Although the sequence of element B is highly similar to those of S pl binding sites, it does not bind Spl 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 nucl eotides. The activity of the phospholipase A, promoter in HeLa cells w as lower than in HepG2 cells, and was correlated with the absence of c omplex 3 in HeLa cell nuclear extracts. Our results suggest different roles for the proteins bound to the 5'-GACCACGCC-3' sequence. In parti cular, the 75-kDa protein which forms the third complex is critical fo r the activity of the promoter of the secretory phospholipase A(2) gen e.