GENE ORGANIZATION AND PROMOTER FUNCTION FOR CC-CHEMOKINE RECEPTOR-5 (CCR5)

CC chemokine receptor 5 (CCR5) functions physiologically as a receptor for the leukocyte chemoattractants macrophage inflammatory protein-1 alpha, macrophage inflammatory protein-1 beta, and RANTES, and functio ns pathologically as a key cell entry coreceptor for HIV-1?. The facto rs that regulate CCR5 expression may be useful therapeutic targets for HIV-I infection. To identify nuclear regulatory factors, we have loca ted and functionally characterized the CCR5 gene promoter. The gene co nsists of two exons separated by a 1.9-kb intron. Exon I contains 43 b p of the 5'-untranslated region; exon 2 contains Il bp of the 5'-untra nslated region and the complete open reading frame. primer extension a nalysis identified two adjacent transcriptional start points (tsp) tha t map to the first 2 bp found in the longest known CCR5 cDNA sequence. A TATA box is present 31 bp upstream from the first tsp. CCR5 mRNA wa s detected constitutively in both primary human myeloid and lymphoid c ells by Northern blot hybridization. Consistent with this, transcripti on of a chloramphenicol acetyltransferase reporter gene was constituti vely activated in both transiently transfected myeloid and lymphoid ce ll lines by the 80-bp gene fragment located immediately upstream of th e tsp. Deletion analysis located a strong silencer element between nuc leotides -244 and -80, and a strong enhancer element between -486 and -244. These results suggest that the gene region between -486 and -1 m ay regulate the expression of CCR5 in monocyte/macrophages and T lymph ocytes.