NOVEL ELEMENTS LOCATED AT -504 TO -399 BP OF THE PROMOTER REGION REGULATED THE EXPRESSION OF THE HUMAN MACROPHAGE SCAVENGER RECEPTOR GENE IN MURINE MACROPHAGES

The expressions of type I and type II macrophage scavenger receptors ( MSRs) are highly specific in macrophages and related cell types. Altho ugh some reports have described the regulation of MSR gene expression and proposed some cis-elements related to cell-specific expression, th e regulation of MSR remains largely unclear. This is due, in part, to an unacceptably low efficiency of transfection into monocyte/macrophag e cells. In the present study, we optimized the conditions of electrop oration in murine macrophage (P388D1) cells. The efficiency of electro poration was increased 20-fold compared with previous methods. Using t he optimized method, we focused on studying the regulation of the huma n MSR promoter in macrophages. We presently demonstrate that: a) the p roximal -10 to +50 bp human MSR promoter region is necessary for the c ell type-specific expression of human MSR; b) the 6.5 kbp upstream seq uence suppresses the expression of human MSR; c) a promoter region ext ending from -504 to -399 bp produced the greatest increase in transcri ptional activity; (I) macrophage cell-specific transcription factors b ind to the region as determined by electrophoretic mobility shift assa y (EMSA) and a footprint assay; and e) mutations of the region reduced about 40-15% of the promoter activity in a transfecting assay. We con cluded that novel elements located at the -504 to -399 bp region may p lay an a important role in the regulation of the MSR gene expression i n macrophages. We speculate that macrophage-specific factors binding t o those elements may be responsible for the transcription regulation o f the MSR gene in macrophages.