Stanley Mark Hollenberg

Colocalization of DNA-binding and transcriptional activation functions in the human glucocorticoid receptor

Using a combination of a transient expression assay and in vitro mutagenesis, we showed previously that the human glucocorticoid receptor (hGR) is composed of a series of discrete functional domains. Here we report the effects of selective deletion of each of these domains on hGR ability to activate transcription of the MTV-CAT fusion gene. Deletion of the immunogenic domain or the entire amino-terminal half of the protein reduces but does not abolish the ability of the hGR to induce transcriptional activation. Somewhat surprisingly, deletion of the steroid-binding domain engenders a constitutively active receptor, revealing that this domain normally represses receptor function. However, the central, cysteine-rich region contains all the information required for both DNA binding and trans-activation. Taken together, these data delineate a core domain in the hGR spanning 88 amino acids that determines both DNA-binding and transcriptional activation functions. This physical linkage distinguishes the glucocorticoid receptor from other described eukaryotic regulatory proteins, where these two functions have been shown to be separable.

Developmental and Hormonal Regulation of Neuroendocrine Gene Transcription

Publisher Summary The quantitative regulation of gene transcription during development and by hormones appears to require the interaction of specific rate-limiting transcriptional factors that bind to structurally distinct genomic sequences. The precise molecular mechanisms by which the binding of these trans-acting factors increases the rate of accurate transcriptional initiation remain unknown; however, it is clear that the regulatory cis-active regions can represent either simple or complex elements. In the case of heritable patterns of neuroendocrine expression, a combinatorial reaction of several sequences and their cognate transcription factors appears requisite for cell-specific gene transcription. The multi-factorial nature of this regulation provides the possibility for a more restricted pattern of gene expression than that exhibited by the cognate trans-acting transcription factors. In the case of the rat prolactin gene, three to five discrete factors may be required for the upstream enhancer function. Additional important cell-specific enhancers appear to be present in proximity to the promoter. By contrast, several regulatory cis-active elements, such as those that transfer hormone regulation, appear to bind a unique transcription factor, which may be sufficient for activation of gene transcription.