Binding of @entity18720 and ETS-domain family members is associated with enhancer activity in the hypersensitive site III region of the XXXX growth hormone/chorionic somatomammotropin locus.

@entity1 @entity2036 @entity5 @entity2498 @entity8682 @entity18720
The @entity1 GH gene family is specifically expressed in somatotrophs of the anterior pituitary and placental syncytiotrophoblast. Two nuclease-hypersensitive sites, @entity8682 , are associated with a region of chromatin located 28 and 30 kb upstream of the pituitary GH gene transcription initiation site (+1) in both pituitary and placenta nuclei. A role for this region in pituitary GH gene expression has been reported, but the potential relevance to placental gene expression has not been determined. Deletion analysis of a 5.2-kb region ( @entity2036 - 27,568/-32,746) containing @entity8682 III to V-related sequences localized significant enhancer activity to a 574-bp @entity8682 III fragment ( @entity2036 -27,676/-28,249) in multiple transfected cell lines. Four nuclease-protected regions [footprints (FP) 1-4] were identified in the 574-bp fragment. FP2 and FP3 were detected with placenta cell nuclear protein, whereas FP1 and FP4 were observed with placental and nonplacental cell nuclear extract. Disruption of FP1 had no effect on heterologous promoter activity in transfected pituitary and placental cells, whereas loss of FP2 and FP3 resulted in modest increases in placental cells, reflecting the presence of repressor activity associated with these regions in vitro. In contrast, disruption of the FP4 region by mutation or deletion significantly reduced enhancer activity. As a result, 30-fold enhancer activity was localized to a 41-bp region in transfected @entity5 cells. Binding of candidate proteins, activator protein (AP)-2 (FP3) and @entity2498 -1 (FP4), was confirmed using competition assays with specific oligonucleotides and antibodies. Moreover, these factors were associated with the hyperacetylated @entity8682 III region in @entity1 pituitary [ @entity18720 ( @entity18720 ) and @entity2498 -1] and term placenta ( @entity18720 ) chromatin. These data implicate @entity18720 and ETS-domain family members in the regulation of the GH/CS locus and raise the possibility that different complexes form in the @entity8682 III region in placenta and pituitary cells.
