The DNA-binding and tau2 transactivation domains of the rat glucocorticoid receptor constitute a nuclear matrix-targeting signal.
Using an ATP-depletion paradigm to augment glucocorticoid receptor (GR) binding to the nuclear matrix, we have identified a minimal segment of the receptor that constitutes a nuclear matrix targeting signal (NMTS). While previous studies implicated a role for the receptor's DNA-binding domain in nuclear matrix targeting, we show here that this domain of rat GR is necessary, but not sufficient, for matrix targeting. A minimal NMTS can be generated by linking the rat GR DNA-binding domain to either its tau2 transactivation domain in its natural context, or a heterologous transactivation domain derived from the Herpes simplex virus VP16 protein. The transactivation and nuclear matrix-targeting activities of tau2 are separable, as transactivation mutants were identified that either inhibited or had no apparent effect on matrix targeting of tau2. A functional interaction between the NMTS of rat GR and the RNA-binding nuclear matrix protein hnRNP U was revealed in cotransfection experiments in which hnRNP U overexpression was found to interfere with the transactivation activity of GR derivatives that possess nuclear matrix-binding capacity. We have therefore ascribed a novel function to a steroid hormone transactivation domain that could be an important component of the mechanism used by steroid hormone receptors to regulate genes in their native configuration within the nucleus.
Tang
Y
Y
Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA.
Getzenberg
R H
RH
Vietmeier
B N
BN
Stallcup
M R
MR
Eggert
M
M
Renkawitz
R
R
DeFranco
D B
DB
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000378:metabolism*; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D019913:Nuclear Localization Signals; D012313:RNA / Q000378:metabolism; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism; D015533:Transcriptional Activation
D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D019913:Nuclear Localization Signals; D011965:Receptors, Glucocorticoid; D012261:Ribonucleoproteins; D012313:RNA; D000255:Adenosine Triphosphate; D004247:DNA