Protein coding genes, expression control elements

The various transcription-control elements found in eukaryotic DNA are binding sites for regulatory proteins. In this section, we discuss the identification, purification, and structures of these transcription factors, which function to activate or repress expression of eukaryotic protein-coding genes. 

Thyroid hormone binds to receptors in the nucleus that control the expression of genes responsible for many metabolic processes. The T3 receptor exists in two monomeric forms alpha and beta. When activated by T3, the a and (3 monomers combine to form ao, PP, or aP dimers. These Tj-activated dimers bind to DNA response elements and control the synthesis of RNA, which codes for specific proteins that mediate the actions of thyroid hormones. 

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