Hagen S G, Larson R J, Strait K A, Oppenheimer J H
Department of Medicine, University of Minnesota, Minneapolis 55455, USA.
J Mol Neurosci. 1996 Winter;7(4):245-55. doi: 10.1007/BF02737062.
Two thyroid hormone response elements (TREs), designated A1 TRE (-295/-268) and B1 TRE (+207/+227), have been identified within the Purkinje cell-expressed Pcp-2 gene. Previous studies have characterized the A1 TRE (Zou et al., 1994). This article analyzes the structural and functional characteristics of the intronic B1 TRE. The B1 sequence contains four overlapping TRE half-sites. The 3' DR4 motif, consisting of the second and forth half-sites, is responsible for the T3 induction observed with the B1 sequence. Gel-shift analysis reveals developmentally regulated complexes that are abundant in the fetus and at birth and then fall precipitously in the neonate bind to B1. The observed time-course of these complexes varies inversely with the rise in Pcp-2 expression, thus raising the possibility that the complexes may represent inhibitory factors. Supershift analysis indicates that endogenous TR alpha 1 is present in the fetal nuclear protein complexes that bind to B1. Competition analysis also indicates the second B1 TRE half-site is important in binding the TR alpha 1-TRAP complexes. These studies suggest that the B1 sequence may bind potential TR alpha 1-TRAP repressor complexes in the fetus, whereas in the neonate, these TRE sites may be involved in the activation of Pcp-2 by binding other TR-TRAP-activating complexes.
在浦肯野细胞表达的Pcp-2基因中已鉴定出两个甲状腺激素反应元件（TRE），分别命名为A1 TRE（-295 / -268）和B1 TRE（+207 / +227）。先前的研究已对A1 TRE进行了表征（邹等人，1994年）。本文分析了内含子B1 TRE的结构和功能特征。B1序列包含四个重叠的TRE半位点。由第二个和第四个半位点组成的3'DR4基序负责B1序列所观察到的T3诱导。凝胶迁移分析显示，在胎儿期和出生时丰富、然后在新生儿期急剧下降的发育调控复合物与B1结合。观察到的这些复合物的时间进程与Pcp-2表达的升高呈反比，因此增加了这些复合物可能代表抑制因子的可能性。超迁移分析表明，内源性TRα1存在于与B1结合的胎儿核蛋白复合物中。竞争分析还表明，第二个B1 TRE半位点在结合TRα1-TRAP复合物中很重要。这些研究表明，B1序列可能在胎儿期结合潜在的TRα1-TRAP阻遏复合物，而在新生儿期，这些TRE位点可能通过结合其他TR-TRAP激活复合物参与Pcp-2的激活。
