A distinct modulating domain in glucocorticoid receptor monomers in the repression of activity of the transcription factor AP-1.

Steroid receptors activate and repress genes. An important class of genes that they repress is controlled by the transcription factor AP-1. The activity of AP-1 is inhibited by the receptor, a mechanism exploited for the therapy of various forms of pathological hyperproliferation in humans. We show here by point mutations in the DNA binding domain and by the choice of steroid ligands that repression of AP-1 activity and transactivation functions of the glucocorticoid receptor (GR) are separable entities. While DNA binding and activation of glucocorticoid-regulated promoters require GR dimerization, we present data that suggest that repression is a function of GR monomers.