Palindromic sequences glucocorticoid receptor binding

The individual domains of the two receptors both have structures similar to that of the glucocorticoid receptor, and they bind to DNA in a similar way, with their recognition helices in the major groove. The dimer contacts are, however, totally different. In the glucocorticoid receptor, which binds to a palindromic DNA sequence like the 434 repressor described in Chapter 8, the domains interact symmetrically in a head-to-head fashion equivalent... 

The HREs of the steroid hormone receptors posses a palindromic structure, comparable to the DNA binding elements of procaryotic repressors (see fig. 4.7a). The glucocorticoid receptor, for example, binds as a homodimer to the two-fold symmetrical recognition sequence, whereby the receptor is already dimerized in solution. In complex with the DNA each subimit of the dimer contacts one half-site of the HRE. As a consequence of the two-fold repeat of the recognition sequence, a high affinity binding of the receptor dimer results (compare 1.2.4). 

The response elements for glucocorticoids and estrogen receptors contain short palindromic sequences with various three-nucleotide "spacer" sequences in the center as follows.308,314,316-318 Two receptor proteins bind to the palindromic DNA forming a ho-modimeric receptor pair. For the 9-cis retinoic acid receptor RXR-a the response element contains a pair of direct repeats of a 6-base consensus sequence with a two-base pair spacer ... 

In the nucleus, the hormone-receptor complex binds to nucleotide sequences known as hormone response elements (HREs). These are short palindromic DNA segments that usually promote transcription as enhancer elements (see p. 244). The illustration shows the HRE for glucocorticoids (GRE ... 

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