Thyroid hormone receptor (TR) regulates growth, development, and differentiation of mammals. TR contains both a domain that binds to T3, the thyroid hormone, and a separate domain that binds to the DNA. Which of the following BEST explains how TR signals?
TR signals by binding to T3 and then binding to DNA.
When T3 hormone is not bound to TR, TR remains inactive. However, when T3 hormone binds to the T3-binding domain of TR, a conformational change occurs and activates TR. This activated TR can then bind to specific DNA sequences known as thyroid hormone response elements (TREs) through its DNA-binding domain.
Once TR is bound to TREs, it can recruit coactivator proteins to initiate gene transcription and regulate the expression of target genes. This ultimately leads to the growth, development, and differentiation of mammals as regulated by thyroid hormone.
Therefore, the binding of T3 to TR is crucial for the activation of TR and its subsequent binding to the DNA to control gene expression.