Research resource: identification of novel coregulators specific for thyroid hormone receptor-ß2.

Thyroid hormone receptors (TRs) are expressed as a series of interrelated isoforms that perform distinct biological roles. The TRß2 isoform is found predominantly in the hypothalamus, pituitary, retina, and cochlea and displays unique transcriptional properties relative to the other TR isoforms. To more fully understand the isoform-specific biological and molecular properties of TRß2, we have identified a series of previously unrecognized proteins that selectively interact with TRß2 compared with the more widely expressed TRß1. Several of these proteins preferentially enhance the transcriptional activity of TRß2 when coexpressed in cells and are likely to represent novel, isoform-specific coactivators. Additional proteins were also identified in our screen that bind equally to TRß1 and TRß2 and may function as isoform-independent auxiliary proteins for these and/or other nuclear receptors. We propose that a combination of isoform-specific recruitment and tissue-specific expression of these newly identified coregulator candidates serves to customize TR function for different biological purposes in different cell types.