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

J. Biol. Chem., Vol. 281, Issue 39, 29337-29348, September 29, 2006

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 281/39/29337    most recent M604271200v1 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 Anders, A. Articles by Breunig, K. D. Search for Related Content PubMed PubMed Citation Articles by Anders, A. Articles by Breunig, K. D. Social Bookmarking                      What's this?

The Galactose Switch in Kluyveromyces lactis Depends on Nuclear Competition between Gal4 and Gal1 for Gal80 Binding^*

Alexander Anders, Hauke Lilie, Kathlen Franke¹, Lutz Kapp², Jörg Stelling^¶3, Ernst D. Gilles^¶, and Karin D. Breunig⁴

From the Institut für Genetik and Institut für Biotechnologie, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle, Germany and ^¶Max-Planck-Institut für Dynamik Komplexer Technischer Systeme, 39106 Magdeburg, Germany

The Gal4 protein represents a universally functional transcription activator, which in yeast is regulated by protein-protein interaction of its transcription activation domain with the inhibitor Gal80. Gal80 inhibition is relieved via galactose-mediated Gal80-Gal1-Gal3 interaction. The Gal4-Gal80-Gal1/3 regulatory module is conserved between Saccharomyces cerevisiae and Kluyveromyces lactis. Here we demonstrate that K. lactis Gal80 (KlGal80) is a nuclear protein independent of the Gal4 activity status, whereas KlGal1 is detected throughout the entire cell, which implies that KlGal80 and KlGal1 interact in the nucleus. Consistently KlGal1 accumulates in the nucleus upon KlGAL80 overexpression. Furthermore, we show that the KlGal80-KlGal1 interaction blocks the galactokinase activity of KlGal1 and is incompatible with KlGal80-KlGal4-AD interaction. Thus, we propose that dissociation of KlGal80 from the AD forms the basis of KlGal4 activation in K. lactis. Quantitation of the dissociation constants for the KlGal80 complexes gives a much lower affinity for KlGal1 as compared with Gal4. Mathematical modeling shows that with these affinities a switch based on competition between Gal1 and Gal4 for Gal80 binding is nevertheless efficient provided two monomeric Gal1 molecules interact with dimeric Gal80. Consistent with such a mechanism, analysis of the sedimentation behavior by analytical ultracentrifugation demonstrates the formation of a heterotetrameric KlGal80-KlGal1 complex of 2:2 stoichiometry.

Received for publication, May 4, 2006 , and in revised form, July 12, 2006.

^* This was supported by Deutsche Forschungsgemeinschaft Grant Br 921/4-2 (to K. D. B.) and by Land Sachsen-Anhalt Grant 3326A/0021M (to K. D. B.). 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.

The on-line version of this article (available at http://www.jbc.org) contains Fig. S1 and Table S1.

¹ Present address: Gemeinschaftspraxis Prager/Junge/Hennig/Linné, Friedrichstrasse 38/40, 01067 Dresden, Germany.

² Present address: Qiagen GmbH, 40724 Hilden, Germany.

³ Present address: Institute of Computational Science, ETH Zurich, 8092 Zurich, Switzerland.

⁴ To whom correspondence should be addressed. Tel.: 49-0345-5526304; Fax: 49-0345-5527151; E-mail: karin.breunig{at}genetik.uni-halle.de.

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

This article has been cited by other articles:

				C. A. Sellick, T. A. Jowitt, and R. J. Reece The Effect of Ligand Binding on the Galactokinase Activity of Yeast Gal1p and Its Ability to Activate Transcription J. Biol. Chem., January 2, 2009; 284(1): 229 - 236. [Abstract] [Full Text] [PDF]

				R. Wightman, R. Bell, and R. J. Reece Localization and Interaction of the Proteins Constituting the GAL Genetic Switch in Saccharomyces cerevisiae Eukaryot. Cell, December 1, 2008; 7(12): 2061 - 2068. [Abstract] [Full Text] [PDF]

				C. Gancedo and C.-L. Flores Moonlighting Proteins in Yeasts Microbiol. Mol. Biol. Rev., March 1, 2008; 72(1): 197 - 210. [Abstract] [Full Text] [PDF]

				J. B. Thoden, C. A. Sellick, R. J. Reece, and H. M. Holden Understanding a Transcriptional Paradigm at the Molecular Level: THE STRUCTURE OF YEAST Gal80p J. Biol. Chem., January 19, 2007; 282(3): 1534 - 1538. [Abstract] [Full Text] [PDF]