title: Regulation of mouse small heat shock protein αb-crystallin gene by aryl hydrocarbon receptor.
abstract: The stress-inducible small heat shock protein (shsp)/αB-crystallin gene is expressed highly in the lens and moderately in other tissues. Here we provide evidence that it is a target gene of the aryl hydrocarbon receptor (AhR) transcription factor. A sequence (-329/-323, CATGCGA) similar to the consensus xenobiotic responsive element (XRE), called here XRE-like, is present in the αBE2 region of αB-crystallin enhancer and can bind AhR in vitro and in vivo. αB-crystallin protein levels were reduced in retina, lens, cornea, heart, skeletal muscle and cultured muscle fibroblasts of AhR(-/-) mice; αB-crystallin mRNA levels were reduced in the eye, heart and skeletal muscle of AhR(-/-) mice. Increased AhR stimulated αB-crystallin expression in transfection experiments conducted in conjunction with the aryl hydrocarbon receptor nuclear translocator (ARNT) and decreased AhR reduced αB-crystallin expression. AhR effect on aB-crystallin promoter activity was cell-dependent in transfection experiments. AhR up-regulated αB-crystallin promoter activity in transfected HeLa, NIH3T3 and COS-7 cells in the absence of exogenously added ligand (TCDD), but had no effect on the αB-crystallin promoter in C(2)C(12), CV-1 or Hepa-1 cells with or without TCDD. TCDD enhanced AhR-stimulated αB-crystallin promoter activity in transfected αTN4 cells. AhR could bind to an XRE-like site in the αB-crystallin enhancer in vitro and in vivo. Finally, site-specific mutagenesis experiments showed that the XRE-like motif was necessary for both basal and maximal AhR-induction of αB-crystallin promoter activity. Our data strongly suggest that AhR is a regulator of αB-crystallin gene expression and provide new avenues of research for the mechanism of tissue-specific αB-crystallin gene regulation under normal and physiologically stressed conditions.
authors.affiliation: Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America. liushuang1999@yahoo.com
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.forename: Joram
authors.initials: J
authors.lastname: Piatigorsky
mesh_terms: D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive / Q000187:drug effects; D021901:DNA, Intergenic / Q000235:genetics; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D055551:HSP27 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000187:drug effects; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000172:deficiency / Q000378:metabolism*; D038203:alpha-Crystallin B Chain / Q000235:genetics* / Q000378:metabolism
chemical_list: C525420:Cryab protein, mouse; D021901:DNA, Intergenic; D055551:HSP27 Heat-Shock Proteins; C486699:Hspb2 protein, mouse; D008024:Ligands; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D038203:alpha-Crystallin B Chain; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator