Cutting edge: chromatin remodeling at the IL-4/IL-13 intergenic regulatory region for Th2-specific cytokine gene cluster

During the differentiation of naive Th cells into Th2 effector cells, the entire IL-4/IL-13 locus is remodeled into an accessible chromatin conformation. Here we show that ectopic expression and activation of Stat6 or GATA-3 in Th cells developing under Th1-polarizing conditions lead to the induction of chromatin remodeling not only at the flanking regions of the IL-4 and IL-13 genes but also at the IL-4/IL-13 intergenic regulatory region for the IL-4/IL-13/IL-5 gene cluster. Furthermore, we demonstrate that GATA-3 and another Th2-specific, inducible protein complex interact with the IL-4/IL-13 intergenic DNase I hypersensitive region specifically in Th2 cells.     

Chromatin structure at the flanking regions of the human beta-globin locus control region DNase I hypersensitive site-2: proposed nucleosome positioning by DNA-binding proteins including GATA-1

The human beta-globin locus control region DNase I hypersensitive site-2 (LCR HS-2) is erythroid-specific and is located 10.9 kb upstream of the epsilon-globin gene. Most studies have only examined the core region of HS-2. However, previous studies in this laboratory indicate that positioned nucleosomes are present at the 5'- and 3'-flanking regions of HS-2. In addition, footprints were observed that indicated the involvement of DNA-binding proteins in positioning the nucleosome cores. A consensus GATA-1 site exists in the region of the 3'-footprint. In this study, using an electrophoretic mobility shift assay (EMSA) and DNase I footprinting, we confirmed that GATA-1 binds in vitro at the 3'-end of HS-2. An additional GATA-1 site was found to bind GATA-1 in vitro at a site positioned 40 bp upstream. At the 5'-end of HS-2, DNase I footprinting revealed a series of footprints showing a marked correlation with the in vivo footprints. EMSA indicated the presence of several erythroid-specific complexes in this region including GATA-1 binding. Sequence alignment for 12 mammalian species in HS-2 confirmed that the highest conservation to be in the HS-2 core. However, a second level of conservation extends from the core to the sites of the proposed positioning proteins at the HS-2 flanking regions, before declining rapidly. This indicates the importance of the HS-2 flanking regions and supports the proposal of nucleosome positioning proteins in these regions.