HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 281, Issue 33, 23870-23879, August 18, 2006

This Article Full Text Full Text (PDF) All Versions of this Article: 281/33/23870    most recent M602556200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tong, E. H. Y. Articles by Ko, B. C. B. Search for Related Content PubMed PubMed Citation Articles by Tong, E. H. Y. Articles by Ko, B. C. B. Related Collections Related Webpages Social Bookmarking                      What's this?

F1000 Medicine *Must Read* - FREE!

Regulation of Nucleocytoplasmic Trafficking of Transcription Factor OREBP/TonEBP/NFAT5^*

Edith H. Y. Tong, Jin-Jun Guo^¶, Ai-Long Huang^¶, Han Liu^||, Chang-Deng Hu^||, Stephen S. M. Chung^**1, and Ben C. B. Ko²

From the Department of Chemistry, Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, and the ^**Department of Physiology, the University of Hong Kong, Hong Kong Special Administrative Region, China, ^¶Key Laboratory of Molecular Biology on Infectious Diseases, Ministry of Education, Institute for Viral Hepatitis, Chongqing University of Medical Sciences, Chong Qing, China, and the ^||Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University School of Pharmacy, West Lafayette, Indiana 47907

The osmotic response element-binding protein (OREBP), also known as tonicity enhancer-binding protein (TonEBP) or NFAT5, regulates the hypertonicity-induced expression of a battery of genes crucial for the adaptation of mammalian cells to extracellular hypertonic stress. The activity of OREBP/TonEBP is regulated at multiple levels, including nucleocytoplasmic trafficking. OREBP/TonEBP protein can be detected in both the cytoplasm and nucleus under isotonic conditions, although it accumulates exclusively in the nucleus or cytoplasm when subjected to hypertonic or hypotonic challenges, respectively. Using immunocytochemistry and green fluorescent protein fusions, the protein domains that determine its subcellular localization were identified and characterized. We found that OREBP/TonEBP nuclear import is regulated by a nuclear localization signal. However, under isotonic conditions, nuclear export of OREBP/TonEBP is mediated by a CRM1-dependent, leucine-rich canonical nuclear export sequence (NES) located in the N terminus. Disruption of NES by site-directed mutagenesis yielded a mutant OREBP/TonEBP protein that accumulated in the nucleus under isotonic conditions but remained a target for hypotonicity-induced nuclear export. More importantly, a putative auxiliary export domain distal to the NES was identified. Disruption of the auxiliary export domain alone is sufficient to abolish the nuclear export of OREBP/TonEBP induced by hypotonicity. By using bimolecular fluorescence complementation assay, we showed that CRM1 interacts with OREBP/TonEBP, but not with a mutant protein deficient in NES. Our findings provide insight into how nucleocytoplasmic trafficking of OREBP/TonEBP is regulated by changes in extracellular tonicity.

Received for publication, March 20, 2006 , and in revised form, June 16, 2006.

^* This work was supported by the University Grant Committee of the Hong Kong Special Administrative Region Area of Excellence Scheme Grant AoE/P-10/01, by the University of Hong Kong Generic Drugs Research Program, and by Research Grant Council Grants HKU 7419/03 M and 7427/04 M (to B. C. B. K.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence may be addressed. E-mail: smchung{at}hkucc.hku.hk.

² To whom correspondence may be addressed. E-mail: cbko{at}hkucc.hku.hk.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

Related Webpages: