STRUCTURE OF THE MURINE MACROPHAGE SCAVENGER RECEPTOR GENE AND EVALUATION OF SEQUENCES THAT REGULATE EXPRESSION IN THE MACROPHAGE CELL-LINE, P388D(1)

The structure of the entire murine scavenger receptor gene was determi ned; it consists of eleven exons spanning more than 60 kilobases. Prim er extension showed that transcription initiates at a cluster of sites unassociated with a TATAA element. DNA sequences adjacent to these tr anscription start sites are highly conserved in murine, human, and bov ine genes. When transcriptional activity was tested using a luciferase reporter gene, a promoter fragment (-124 to +20) stimulated luciferas e production in P388D(1) macrophage-like cells but not in non-macropha ge COS-7 or 3T3 cells. A longer promoter fragment (approximately 5 kb) stimulated luciferase activity a further 10-fold in P388D(1) cells. H owever, using a series of fragments from -67 to -1500 bp, a 127 bp fra gment (-67 to +50) was as active as a 1500 bp fragment in these assays . Mutation of a putative AP-1 element in the -67 to +50 promoter fragm ent reduced luciferase activity by 40%; mutation of a putative GATA fa ctor element to TATA increased luciferase activity nearly 2-fold while mutation to AATA had no effect and deletion of the GATA sequence inhi bited activity by about 50%. The results suggest that a scavenger rece ptor promoter fragment can confer cell-specific transcription and that the activity may be mediated in part by factors that recognize the AP -1 and GATA elements.