DOMAINS OF THE HUMAN ANDROGEN RECEPTOR AND GLUCOCORTICOID RECEPTOR INVOLVED IN BINDING TO THE NUCLEAR MATRIX

Steroid receptors have been reported to bind to the nuclear matrix. Th e nuclear matrix is operationally defined as the residual nuclear stru cture that remains after extraction of most of the chromatin and all s oluble and loosely bound components. To obtain insight in the molecula r mechanism of the interaction of steroid receptors with the nuclear m atrix, we studied the binding of several deletion mutants of the human androgen receptor (hAR) and the human glucocorticoid receptor (hGR) t o the nuclear matrix. Receptor binding was tested for two different nu clear matrix preparations: complete matrices, in which most matrix pro teins are retained during the isolation procedure, and depleted matric es, which consist of on ly a subset of these protei ns. The results sh ow that the C-terminal domain of the hAR binds tightly to both deplete d and complete matrices. In addition, at least one other domain of the hAR binds to complete matrices but not to depleted matrices. In contr ast to the hAR, the hGR binds only to complete matrices. For this inte raction both the DNA-binding domain and the C-terminal domain of the h GR are required, whereas the N-terminal domain is not. We conclude tha t specific protein domains of the hAR and the hGR are involved in bind ing to the nuclear matrix. In addition, our results indicate that the hAR and the hGR are attached to the nuclear matrix through different m olecular interactions. (C) 1995 Wiley-Liss, Inc.