Figure 4.
T3 and TSA induce transcription of T3 response genes without altering TR/RXR binding to TRE in premetamorphic tadpoles. (A) Differential effects of T3 and TSA on gene expression. Stage 55 tadpoles were treated for 2 days with T3 (10 nM) or TSA (100 nM). Total RNA was extracted from whole animals, intestine, or tail tissues and used for PCR analysis of TRβ and TH/bZIP expression. The expression of ribosomal protein gene Rpl8 was used as an internal control. Note that T3 treatment increased mRNA levels of T3 response genes in whole animals, intestine, and tail, whereas TSA treatment altered T3 response gene expression only in intestine and tail. (B) TR/RXR binds to TREs in chromatin constitutively. Chromatin isolated from whole tadpoles, the intestine, or the tail of the T3- or TSA-treated stage 55 tadpoles (A) was immunoprecipitated with antibodies against TR or RXR and analyzed by PCR as in Fig. 2. The figure represents one of two independent experiments with identical results.