Dimerization of Cdc25p, the Guanine-Nucleotide Exchange Factor for Ras from Saccharomyces Cerevisiae, and its Interaction with Sdc25p

Authors

  • Christelle Camusi,

    1. Laboratoire Information Génétique et DCveloppement, Institut de GénCtique et Microbiologie, URA CNRS 2225, Universitt Paris-Sud, France
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  • Marco Geymonat,

    1. Laboratoire Information Génétique et DCveloppement, Institut de GénCtique et Microbiologie, URA CNRS 2225, Universitt Paris-Sud, France
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  • Hervé Garreau,

    1. Laboratoire Information Génétique et DCveloppement, Institut de GénCtique et Microbiologie, URA CNRS 2225, Universitt Paris-Sud, France
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  • Sylvie Baudet-Nessler,

    1. Laboratoire d'Enzymologie et Biologie Structurale, UPR CNRS 9063, Gif-sur-Yvette, France
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  • Michel Jacqueti

    Corresponding author
    1. Laboratoire Information Génétique et DCveloppement, Institut de GénCtique et Microbiologie, URA CNRS 2225, Universitt Paris-Sud, France
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M. Jacquet, Lahoratoire Information Gtnttique et DCveloppement, Institut de Génétique et Microbiologie, URA CNRS 2225, Bátiment 400, Université Paris-Sud, F-91405 Orsay, France
Fax:+33 1 6915 7296.
E-mail:jacquetaigm0rs.u-psud.fr

Abstract

The oligomerization state of Cdc25p, the guanine nucleotide exchange factor for ras from yeast, was analyzed using different complementary approaches. The two-hybrid system showed that the C-terminal part of Cdc25p (Cdc25-Ct) can interact with itself but also with Sdc25p-Ct, the corresponding part of Sdc25p, the other guanine exchange factor from yeast. The homotropic interaction of Cdc25p-Ct has been confirmed in yeast using immunoprecipitation experiments with epitope-tagged and P-galactosidase-fused polypeptides. No other component was required for this interaction, since dimerization was shown to occur with material synthesized in vitro. The size of Cdc25-Ct produced in Escherichia coli has been directly measured on gel filtration columns and corresponds to a dimer. The dimerization domain is localized in the same part of the molecule as the catalytic domain and the portion responsible for membrane localization. The biological relevance of dimerization is still an open question, however by allowing heterodimerization with Sdc25p it could permit a more complex cornbinatorial regulation of ras in yeast.

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