Progestin response element

Fig. 5. Specificity of steroid response element. A. In this example (mouse mammary tumour virus), the element will bind receptors for glucocorticoids (G), androgen (A), progestin (P) and mineralocorticoid (M) so that each of these classes of steroid stimulate transcription. This type of specificity can vary from cell to cell possibly due to other protein factors (not shown). B. Although oestrogen (E) receptor will not act as an agonist for mouse mammary tumour virus transcription, it may antagonise the agonist activity of glucocorticoids (G).

In the absence of a ligand, PR is associated with a complex of heat shock proteins as a monomer in an inactivated state in the cytosol. When a progestin binds to the receptor, the overall conformation changes. Heat shock proteins are liberated, and the receptor dimerizes, enters into the cell nucleus and binds to selective progesterone-responsive elements (PREs) on the DNA to induce transcriptional activity. 

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