title: Enhancer-blocking activity within the DNase I hypersensitive site 2 to 6 region between the TCR alpha and Dad1 genes.
abstract: Although tightly linked, the TCR alpha and delta genes are expressed specifically in T lymphocytes, whereas the Dad1 gene is ubiquitously expressed. Between TCR alpha and Dad1 are eight DNase I hypersensitive sites (HS). HS1 colocalizes with the TCR alpha enhancer (Ealpha) and is T cell-specific; HS2, -3, -4, -5, and -6 map downstream of HS1 and are tissue-nonspecific. The region spanning HS2-6 was reported to display chromatin-opening activity and to confer copy number-dependent and integration site-independent transgene expression in transgenic mice. Here, we demonstrate that HS2-6 also displays enhancer-blocking activity, as it can block an enhancer from activating a promoter when located between the two in a chromatin-integrated context, and can do so without repressing either the enhancer or the promoter. Multiple enhancer-blocking elements are arrayed across HS2-6. We show that HS2-6 by itself does not activate transcription in chromatin context, but can synergize with an enhancer when located upstream of an enhancer and promoter. We propose that HS2-6 primarily functions as an insulator or boundary element that may be critical for the autonomous regulation of the TCR alpha and Dad1 genes.
authors.affiliation: Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: X P
authors.initials: XP
authors.lastname: Zhong
authors.forename: M S
authors.initials: MS
authors.lastname: Krangel
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D002934:Cinnamates; D003850:Deoxyribonuclease I / Q000378:metabolism*; D004742:Enhancer Elements, Genetic / Q000276:immunology*; D005786:Gene Expression Regulation / Q000276:immunology; D019673:Genes, T-Cell Receptor alpha; D006801:Humans; D006921:Hygromycin B / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D019169:Jurkat Cells; D019901:Locus Control Region / Q000276:immunology; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D009355:Neomycin / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D010957:Plasmids / Q000037:antagonists & inhibitors / Q000138:chemical synthesis; D011401:Promoter Regions, Genetic / Q000276:immunology; D012045:Regulatory Sequences, Nucleic Acid / Q000276:immunology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D002934:Cinnamates; C083331:DAD1 protein, human; C489987:Dad1 protein, mouse; D008565:Membrane Proteins; D006921:Hygromycin B; C026273:hygromycin A; D003850:Deoxyribonuclease I; D009355:Neomycin