REGULAR ARTICLES

Cell Research (2003); 13(6):459-464

Distinct expression profiles of transcriptional coactivators for thyroid hormone receptors during Xenopus laevis metamorphosis

indu D PAUL, Yun-Bo SHI^* Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bldg. USA. E-mail: shi@helix.nih.gov

Received Sep-28-2003 Revised Oct-15-2003 Accepted Oct-25-2003

Abstract

The biological effects of thyroid hormone (T₃) are mediated by the thyroid hormone receptor (TR). Amphibian metamorphosis is one of the most dramatic processes that are dependent on T₃. T₃ regulates a series of orchestrated developmental changes, which ultimately result in the conversion of an aquatic herbivorous tadpole to a terrestrial carnivorous frog. T₃ is presumed to bind to TRs, which in turn recruit coactivators, leading to gene activation. The best-studied coactivators belong to the p160 or SRC family. Members of this family include SRC1/NCoA-1, SRC2/TIF2/GRIP1, and SRC3/pCIP/ACTR/AIB-1/RAC-3/TRAM-1. These SRCs interact directly with liganded TR and function as adapter molecules to recruit other coactivators such as p300/CBP. Here, we studied the expression patterns of these coactivators during various stages of development. Amongst the coactivators cloned in Xenopus laevis, SRC3 was found to be dramatically upregulated during natural and T₃-induced metamorphosis, and SRC2 and p300 are expressed throughout postembryonic development with little change in their expression levels. These results support the view that these coactivators participate in gene regulation by TR during metamorphosis.
Key words: transcription coactivators, thyroid hormone receptor, Xenopus laevis, metamorphosis,
histone acetylation.