Partial overlapping of binding sequences for steroid hormone receptors and DNaseI hypersensitive sites in the rabbit uteroglobin gene region.

Four DNaseI hypersensitive (HS) chromatin regions were found in the uteroglobin locus located at -3.7, -2.4, -0.1 and +4.1 kb with respect to the transcription start site of the gene. The three sites upstream of the gene are only detected in the hormonally stimulated endometrium and disappear after hormone withdrawal, whereas the site at +4.1 is also found in tissues that do not express uteroglobin. In the -2.4 HS region, which is strictly dependent on progesterone treatment, three DNaseI sites are clustered within a 240 bp DNA segment that contains 20 imperfect repeats of an octanucleotide motif. Upstream of the uteroglobin gene there are three regions containing binding sites for the glucocorticoid and the progesterone receptors, located at -3.7, -2.6/-2.7 and -2.4. The -2.4 region contains two binding sites for the hormone receptors flanking the central HS site. In footprinting experiments with naked DNA binding of the receptor also renders this site more susceptible towards digestion with DNaseI. The -2.6/-2.7 region contains three binding sites for the hormone receptors located 140 bp upstream of the HS -2.4. While the -3.7 HS is also located within a receptor binding fragment, there is no binding of the hormone receptors to the promoter region. Thus, interaction of the receptor with DNA sequences far upstream from the promoter alters the chromatin conformation of neighbouring sequences and results in transcriptional activation.