Requirements for the binding of glucocorticoid receptor to octamer transcription factor-1, in vitro.

Abstract

Nuclear receptors and POU transcription factors have been shown to regulate gene transcription through complex cis-acting elements located in upstream promoter regions of target genes. Regulation has been shown to occur through both synergistic and inhibitory mechanisms. Specifically, glucocorticoid dependent transcriptional synergism has been observed within complex regulatory elements on the mouse mammary tumor virus Long Terminal Repeat (MMTV LTR) that contain binding sites for both the glucocorticoid hormone nuclear receptor (GR) and the ubiquitous POU factor, octamer transcription factor-1 (Oct-1). By contrast, on promoters like that of the histone H2B gene that contains regulatory elements only for Oct-1, glucocorticoids actually appear to inhibit the activation of gene transcription by Oct-1. Previous experimental observations were suggestive of a direct physical interaction between the DNA binding domain of GR and the POU DNA binding domain of Oct-1. In this work I have examined the requirements for the binding of in vitro translated, radiolabeled GR to the POU domain of Oct-1 expressed as a glutathione-S-transferase (GST) fusion protein and immobilized on glutathione sepharose. (Abstract shortened by UMI.)