Kevin A. Strait

A purkinje cell protein-2 intronic thyroid hormone response element binds developmentally regulated thyroid hormone receptor-nuclear protein complexes

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 TRα1 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 TRα1-TRAP complexes. These studies suggest that the B1 sequence may bind potential TRα1-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.

Effect of thyroid hormone status on the expression of the mRNAs of components of the lipolytic regulatory cascade in brown adipose tissue.

1. The levels of mRNAs for RII beta and G beta were about 50% lower in brown adipose tissue (BAT) from hyperthyroid than from hypothyroid rats. 2. Treatment of hypothyroid rats with T3 resulted in a 50% decrease in mRNAs for RII beta and G beta in BAT occurring by 12 hr after treatment. 3. The levels of mRNAs for hormone-sensitive lipase, G alpha s and C alpha in BAT were unchanged by thyroid hormone status. 4. The results suggest that thyroid hormone may be involved in negative regulation of the expression of RII beta and G beta at the transcriptional level in BAT.