MCB Download to Citation Manager
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by McGuire, J
Right arrow Articles by Poellinger, L
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by McGuire, J
Right arrow Articles by Poellinger, L
Mol Cell Biol. 1994 April; 14(4): 2438-2446

A cellular factor stimulates ligand-dependent release of hsp90 from the basic helix-loop-helix dioxin receptor.

J McGuire, M L Whitelaw, I Pongratz, J A Gustafsson and L Poellinger

Department of Medical Nutrition, Karolinska Institutet, Huddinge University Hospital, Novum, Sweden.

ABSTRACT

In response to dioxin, the nuclear basic helix-loop-helix (bHLH) dioxin receptor forms a complex with the bHLH partner factor Arnt that regulates target gene transcription by binding to dioxin-responsive sequence motifs. Previously, we have demonstrated that the latent form of dioxin receptor present in extracts from untreated cells is stably associated with molecular chaperone protein hsp90, and Arnt is not a component of this complex. Here, we used a coimmunoprecipitation assay to demonstrate that the in vitro-translated dioxin receptor, but not Arnt, is stably associated with hsp90. Although it showed ligand-binding activity, the in vitro-translated dioxin receptor failed to dissociate from hsp90 upon exposure to ligand. Addition of a specific fraction from wild-type hepatoma cells, however, to the in vitro-expressed receptor promoted dioxin-dependent release of hsp90. This stimulatory effect was mediated via the bHLH dimerization and DNA-binding motif of the receptor. Moreover, ligand-dependent release of hsp90 from the receptor was not promoted by fractionated cytosolic extracts from mutant hepatoma cells which are deficient in the function of bHLH dioxin receptor partner factor Arnt. Thus, our results provide a novel model for regulation of bHLH factor activity and suggest that derepression of the dioxin receptor by ligand-induced release of hsp90 may require bHLH-mediated concomitant recruitment of an additional cellular factor, possibly the structurally related bHLH dimerization partner factor Arnt. In support of this model, addition of in vitro-expressed wild-type Arnt, but not a mutated form of Arnt lacking the bHLH motif, promoted release of hsp90 from the dioxin receptor in the presence of dioxin.

Mol Cell Biol. 1994 April; 14(4): 2438-2446




This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 1994 by the American Society for Microbiology. All rights reserved.