Analysis of the CCR3 promoter reveals a regulatory region in exon 1 that binds GATA-1

In order to define regions responsible for CCR3 transcription, a DNAse hypersensitive site was identified in the vicinity of exon 1. Coupled with our previous data implicating exon 1 in CCR3 transcription, we hypothesized that transcription factors bind to exon-1. Electrophoretic mobility shift analysis revealed that nuclear proteins in eosinophilic cells bound to exon 1. Furthermore, antibody interference and mutation studies demonstrated GATA-1 binding to exon 1. In order to test the 1.6-kb CCR3 promoter element (that includes exon 1) for in vivo function, this region was used to generate transgenic mice that expressed a reporter protein. Strong transgene expression was achieved, with the pattern of expression suggesting a broad acting promoter.The transcription factor GATA-1 binds to CCR3 exon 1. The 1.6-kb CCR3 promoter element, that includes exon 1, is a strong promoter in vivo.CCR3, the eotaxin receptor, is the major chemokine receptor expressed on eosinophils, basophils and a subpopulation of Th2 lymphocytes [1-10]. Recently, CCR3 has been shown to be upregulated on neutrophils and monocytoid U937 cells by interferons in vitro and to be expressed by endothelial cells, epithelial cells and mast cells [11-16]. The relevance of these findings and the function of CCR3 on non-leukocytes remain to be elucidated since the only cells that consistently accumulate following eotaxin administration in vivo are myeloid cells (primarily eosinophils) [17-20].To date, the complete mRNA and genomic organization of only a limited number of chemokine receptors has been described [21-26]. These studies have shown that the 5' untranslated region (5'UTR) can be complex and contain up to 11 exons as in the CXCR2 gene. As a result, alternative splicing and transcription directed by multiple promoters can give rise to variable mRNA isoforms. The function of these 5' untranslated exons has not been examined except for a single study focused on CCR2, demonstrating a transcriptional rol