Pontin52, an interaction partner of β-catenin, binds to the TATA box binding protein

Pontin52, an interaction partner of β-catenin, binds to the TATA box binding protein

Department of Molecular Embryology, Max Planck Institute of Immunobiology, Stübeweg 51, D-79108 Freiburg, Germany

Communicated by Christiane Nüsslein-Volhard, Max Planck Institute for Developmental Biology, Tübingen, Germany (received for review August 13, 1998)

Abstract

β-catenin, the vertebrate homolog of the Drosophila Armadillo protein, has been shown to have dual cellular functions, as a component of both the cadherin-catenin cell adhesion complex and the Wnt signaling pathway. At Wnt signaling, β-catenin becomes stabilized in the cytoplasm and subsequently available for interaction with transcription factors of the lymphocyte enhancer factor-1/T-cell factor family, resulting in a nuclear localization of β-catenin. Although β-catenin does not bind DNA directly, its carboxyl- and amino-terminal regions exhibit a transactivating activity still not well understood molecularly. Here we report the identification of an interaction partner of β-catenin, a nuclear protein designated Pontin52. Pontin52 binds β-catenin in the region of Armadillo repeats 2–5 and, more importantly, also binds the TATA box binding protein. We provide evidence for an in vivo multiprotein complex composed of Pontin52, β-catenin, and lymphocyte enhancer factor-1/T-cell factor. Our results suggest involvement of Pontin52 in the nuclear function of β-catenin.

transcription regulation

Footnotes

↵ * A.B. and O.H. contributed equally to this paper.
↵ † Present address: Institut fuer klinische Chemie, Uniklinik Benjamin Franklin, Hindenburgdamm 30, D-12200 Berlin, Germany.
↵ ‡ To whom reprint requests should be addressed. e-mail: kemler{at}immunbio.mpg.de.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF099084).
ABBREVIATIONS:

LEF-1/TCF,

lymphocyte enhancer factor-1/T-cell factor;

GST,

glutathione S-transferase;

TBP,

TATA box binding protein;

HA,

hemagglutinin