Meeting Abstract
2.4 Jan. 4 Evolutionary conservation of nuclear hormone receptor response elements: thyroid hormone regulation of the basic transcription element binding protein 1 gene. DENVER, Robert/J*; WILLIAMSON, Keith/E; Univ. of Michigan; Univ. of Michigan rdenver@umich.edu
Nuclear hormone receptors (NRs) regulate gene expression by binding to consensus hormone response elements (HREs). HREs may be located within the gene promoter, far upstream of the transcription start site, or within intronic regions. Thyroid hormone (T3) plays critical roles in animal development, and earlier we showed that a T3 responsive gene, basic transcription element binding protein 1 (BTEB1) is induced by the hormone in the brain of tadpoles and neonatal rodents. Furlow and Kanamori (Endocrinology 143:3295) identified a T3 response element (TRE) in the Xenopus laevis BTEB1 gene ~6 kb upstream of the transcription start site. Here we describe the mapping of a TRE in the mouse BTEB1 gene within an evolutionarily conserved region of ~200 base pairs located 3.2 kb upstream of the transcription start site. Gel shift assays showed that TR-RXR heterodimers bound with high affinity to the putative mouse BTEB1 TRE. The TRE acts as a strong response element in transfection assays using a minimal heterologous promoter. In the mouse neuroblastoma cell line N2a[TRβ1], T3 treatment (30 nM) caused rapid upregulation of BTEB1 mRNA. Chromatin immunoprecipitation assay combined with quantitative PCR showed that TRs associated with the mouse BTEB1 TRE in vitro and in vivo, and T3 treatment resulted in hyperacetylation of histones 3 and 4 at the TRE site. Our results identify a functional TRE in the mouse BTEB1 gene, and suggest that natural selection has maintained the structure of this important enhancer element in vertebrates. (Supported by NIH grant 1R01NS046690-01 to R.J.D.)
