Analysis of proteins which specifically binds to thyroid hormone receptor β

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There is a case where any mutations are not found in two types of thyroid hormone receptor(TR) in the resistance to thyroid hormone. We hypothesized that a specific coactivator for thyroid hormone receptor b existed. This coactivator may have any abnormality in the resistance to thyroid hormone. We tried to identify the cDNA for the specific protein. Yeast two-hybrid system was applied to screen a human liver cDNA library. We found two cDNA clones, No.60 and 93, as a candidate of TR-specific coactivator.1. A clone 60 was a fragment derived from 3 kinds of mRNA. The full-length cDNAs for these mRNAs were cloned. The deduced amino acid sequences showed that proteins had nuclear transport signals.2. In amino acid sequences of clone 60 proteins, there was a high homology sequence for another nuclear protein.3. To determine whether a clone 60 protein binds to TRb, pull-down assay was occurred. TRb and a clone 60 protein were expressed as a GST-fusion protein and His-tag fusion protein, respectively. Both fusion protein were mixed and precipitated with specific antibodies. Western blotting showed both fusion proteins bound in vitro.4. A clone 93 could not be expressed as His-tag fusion protein in vitro. We are advancing the analysis of the clone 60 proten further continuously.