A Glucocorticoid Response Element Enhances Transcription of a Methionine tRNA Gene inCisandTrans*

Abstract

In vitro transcription experiments using a Xenopus laevis cell-free extract have demonstrated that a DNA fragment containing a glucocorticoid response element (GRE) significantly enhances the expression of a methionine tRNA gene. This stimulation can be observed when the element is located in cis or trans. In the cis configuration, the element can be located 2900 basepairs from the gene and still display transcriptional enhancement. In trans, the enhancement can occur at a low element to template molecular ratio. The nucleosome positioning and chromatin structure near the tRNA gene appear to be unaffected by the presence of the long terminal repeat of the mouse mammary tumor virus which contains the GRE. Taken together, these data suggest that GREs can stimulate transcription of hormonally unresponsive genes, perhaps by providing a "molecular sink" to which inhibitors may bind. Further experimentation may reveal a correlation between these in vitro studies and in vivo gene regulation.