Transcriptional Regulation by Thyroid Hormone Receptor in Chromatin

Genomic DNA in eukaryotic cells is packaged with histone and nonhistone proteins into chromatin structure. Both biochemical and genetic evidences indicate that chromatin structure imposes constraints on nuclear processes including transcription, replication, recombination and repair (1 ,2 ). Thus, a central question in study of transcription regulation is how transcription factors function in the context of chromatin. In recent years, it has become increasingly clear that chromatin structure has an important role in regulating gene expression and that transcription factors can actively recruit chromatinremodeling enzymes to regulate transcription of their target genes positively or negatively (3 -6 ). In this regard, thyroid hormone receptor (TR) is one of the best-studied transcription factors and has contributed its share of information to the current concept of transcription regulation (7 -9 ).