Th2-specific chromatin remodeling and enhancer activity in the Th2 cytokine locus control region.

We recently identified a 3' region of the rad50 gene possessing strong enhancer activity as well as activity consistent with function as a locus control region (LCR) for the flanking Th2 cytokine genes. In this study, we identify several functional elements within this region by examining chromatin changes as well as activity in transgenic mice. We find within this region four DNase I hypersensitive clusters, three of which are highly conserved and predominantly expressed in Th2 cells. Histone acetylation of this region is elevated in Th2 cells. Further, one of the hypersensitive sites (RHS7) is rapidly demethylated in Th2, but not Th1, cells. In transgenic mice, these hypersensitive sites impart strong, Th2-specific enhancer activity as well as copy number-dependent expression of the reporter gene, recapitulating LCR function. We postulate that these sites function alone or in combination with other regulatory elements to coordinate gene expression in the Th2 cytokine locus.