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Updated: Jul 16, 2026

Repressing Gene Transcription by Redirecting Cellular Machinery with Chemical Epigenetic Modifiers
Published on: September 20, 2018
Patterns of histone acetylation suggest dual pathways for gene activation by a bifunctional locus control region
F Elefant1, Y Su, S A Liebhaber
1Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Abstract:
The five genes of the human growth hormone (hGH) cluster are expressed in either the pituitary or placenta. Activation of the cluster is dependent on a locus control region (LCR) comprising pituitary- specific (HSI,II, -15 kb), placenta-specific (HSIV, -30 kb) and shared (HSIII, -28 kb; HSV, -32 kb) DNase I hypersensitive sites. Gene activation in the pituitary is paralleled by acetylation of a 32 kb chromatin domain 5' to the cluster centered at HSI,II. In the present study we observed that acetylation of this region in placental chromatin was discretely limited to shared HSIII and HSV. Transgenic studies revealed placenta-specific activation of linked genes by a determinant (P-element) located 2 kb 5' to each of the four placentally expressed genes. A localized peak of histone acetylation was observed at these P-elements in placenta but not pituitary. These data support a model for bifunctional action of the hGH LCR in which separate positive determinants, HSI,II and the P-elements, activate their respective target genes by tissue-specific recruitment of distinctly regulated histone acetyl transferase activities.
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