Steroid hormones hormone response element

Hormone response elements (for steroids, T3, retinoic acid, peptides, etc) act as—or in conjunction with— enhancers or silencers (Chapter 43). Other processes that enhance or silence gene expression—such as the response to heat shock, heavy metals (Cd and Zn +), and some toxic chemicals (eg, dioxin)—are mediated through specific regulatory elements. Tissue-specific expression of genes (eg, the albumin gene in liver, the hemoglobin gene in reticulocytes) is also mediated by specific DNA sequences. 

TABLE 28-4 Hormone Response Elements (HREs) Bound by Steroid-Type Hormone Receptors... 

Most recent studies of steroid receptor interactions with nuclear sites have focused on DNA sequences called hormone response elements adjacent to the promoter of... 

Steroid and related hormones bind to specific receptor proteins in the cytosol. The receptor-hormone complexes dimerize and move into the nucleus, where they interact with specific DNA sequences called hormone-responsive elements (HREs). 

Composite AuxREs show some similarity to composite hormone response elements (HREs) found in some animal promoters that respond to steroid hormones [225]. In composite HREs, activator protein-1 (AP-1) or other transcription factor binding sites and... 

A particular group of enhancers are those that are controlled by hormones and are known as hormone response elements. The hormones that directly affect gene expression are those which enter the target tissues, such as steroid hormones, thyroxine and triiodothyronine, and retinoic acid and are discussed further in Chapter 10. 

The level of steroid-induced gene expression from simple promoters containing only hormone response elements and a TATA sequence was not affected by changes in the vitamin Bg status. However, the modulatory influence of vitamin Bg status was restored when a binding site for a transcription factor, nuclear factor (NFI), was included within the hormone-responsive promoter, indicating that PLP modulates gene expression through its influence on a functional interaction between the steroid hormone receptors and transcription factor NFI (71). 

A most important function of vitamin A is in the control of cell differentiation and mrnover. PsA-trans-retinoic acid and 9-cw-retinoic acid (Figure 45-1) regulate growth, development, and tissue differentiation they have different actions in different tissues. Like the steroid hormones and vitamin D, retinoic acid binds to nuclear receptors that bind to response elements of DNA and regulate the transcription of specific genes. There are two families of nuclear retinoid receptors the retinoic acid receptors (RARs) bind all-rrijw-retinoic acid or 9-c -retinoic acid, and the retinoid X receptors (RXRs) bind 9-cw-retinoic acid. 

---