Structural organization of steroid hormone receptors and hormone response elements. Nuclear receptors are multidomain proteins (top, showing the three domains) that bind steroid hormones and DNA to activate transcription. As shown in the enlarged structure of the DNA-binding region (middle), two adjacent zinc fingers bind to the HRE in the DNA (bottom; the binding regions are indicated by dashed lines). The receptors bind the DNA as dimers. The HREs of several steroid hormone receptors are inverted repeats (highlighted in yellow and green).