Structure of the murine macrophage scavenger receptor gene and evaluation of sequences that regulate expression in...

The structure of the entire murine scavenger receptor gene was determined; it consists of eleven exons spanning more than 60 kilobases. Primer extension showed that transcription initiates at a cluster of sites unassociated with a TATAA element. DNA sequences adjacent to these transcription start sites are highly conserved in murine, human, and bovine genes. When transcriptional activity was tested using a luciferase reporter gene, a promoter fragment (-124 to +20) stimulated luciferase production in P388D1 macrophage-like cells but not in non-macrophage COS-7 or 3T3 cells. A longer promoter fragment (approximately 5 kb) stimulated luciferase activity a further 10-fold in P388D1 cells. However, using a series of fragments from -67 to -1500 bp, a 127 bp fragment (-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 fragment reduced luciferase activity by 40%; mutation of a putative GATA factor element to TATA increased luciferase activity nearly 2-fold while mutation to AATA had no effect and deletion of the GATA sequence inhibited activity by about 50%. The results suggest that a scavenger receptor 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.