Mutations in the glucocorticoid receptor zinc finger region that distinguish interdigitated DNA binding and transcriptional enhancement activities.

Mammalian glucocorticoid receptors bind specifically to glucocorticoid response element (GRE) DNA sequences and enhance transcription from GRE-linked promoters in mammalian cells and in yeast. We randomly mutagenized a segment of the receptor encompassing sequences responsible for DNA-binding and transcriptional regulation and screened in yeast for receptor defects. The mutations all mapped to a 66-amino-acid subregion that includes two zinc fingers; in general parallel phenotypes were observed in yeast and animal cells. Mutants defective for DNA binding also failed either to enhance or to repress transcription. However, several mutations in the second finger selectively impaired enhancement; we suggest that such 'positive control' mutants may alter protein-protein contacts required for transcriptional activation.