Mutual Transcriptional Interference between RelA and Androgen Receptor

doi:10.1074/jbc.271.39.24151

Mutual Transcriptional Interference between RelA and Androgen Receptor*

From the Institute of Biomedicine, Department of Physiology, University of Helsinki, FIN-00014 Helsinki, Finland

^‡To whom correspondence should be addressed:
Inst. of Biomedicine, Department of Physiology, P.O. Box 9 (Siltavuorenpenger 20 J), FIN-00014 Helsinki, Finland.
Tel.: 358-9-1918544; Fax: 358-9-1918681; E-mail: olli.janne{at}helsinki.fi

Abstract

Cross-modulation between androgen receptor (AR) and NF-κB/Rel proteins was studied using various androgen- and NF-κB-regulated reporter genes under transient transfection conditions. In COS-1 cells, elevated expression of RelA (p65) repressed AR-mediated transactivation in a dose-dependent manner, whereas NFκB1 (p50), another major member of the NF-κB family, did not influence transactivation. The repression of AR appeared to involve the N-terminal region of the protein between residue 297 and the DNA-binding domain. RelA-mediated transrepression could not be overcome by increasing the amount of AR. Transcriptional interference between RelA and AR was mutual in that cotransfected AR was able to attenuate transactivation by RelA in a dose- and steroid-dependent fashion. An excess of RelA was able to rescue the repression to some extent. Immunological analyses of RelA and AR protein levels indicated that transrepression was not due to reciprocal decrease in their amounts. Neither did AR increase the concentration of IκBα, which can sequester and inactivate RelA. Electrophoretic mobility shift assays using extracts from cotransfected cells and purified recombinant proteins showed that AR and RelA did not significantly influence each other's DNA binding activity. Nevertheless, protein-protein interaction experiments demonstrated a weak association between AR and RelA. Collectively, these data suggest that the mutual repression in intact cells is due to formation of AR-RelA complexes that are held together by another partner or to competition for a coactivator required for transcription.

Footnotes

↵* This work was supported by grants from the Medical Research Council of the Academy of Finland, the Finnish Foundation for Cancer Research, the Sigrid Jusélius Foundation, and the University of Helsinki. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

AR

androgen receptor

ARE

androgen response element

CAT

chloramphenicol acetyltransferase

CMV

cytomegalovirus

DBD

DNA-binding domain

EMSA

electrophoretic mobility shift assay

GR

glucocorticoid receptor

GST

glutathione S-transferase

LBD

ligand-binding domain

LUC

luciferase

MMTV

mouse mammary tumor virus

NT

N-terminal region

IL

interleukin

hAR

human AR

rAR

rat AR.
↵²J. J. Palvimo, P. Reinikainen, and O. A. Jänne, unpublished observations.
↵³T. Ikonen, P. J. Kallio, O. A. Jänne, and J. J. Palvimo, manuscript in preparation.
↵⁴U. Karvonen, P. J. Kallio, J. J. Palvimo, and O. A. Jänne, submitted for publication.
↵⁵P. Reinikainen, and J. J. Palvimo, unpublished observations.
- Received May 3, 1996.
- Revision received July 5, 1996.