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J Biol Chem. 2003 Jul 11;278(28):26135-45. Epub 2003 Apr 24.

Interaction between Smad-interacting protein-1 and the corepressor C-terminal binding protein is dispensable for transcriptional repression of E-cadherin.

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1
Department of Developmental Biology (VIB7), Flanders Interuniversity Institute for Biotechnology (VIB) and Laboratory of Molecular Biology (Celgen), University of Leuven, Herestraat 49, B-3000 Leuven, Belgium.

Abstract

deltaEF1 and SIP1 (or Zfhx1a and Zfhx1b, respectively) are the only known members of the vertebrate Zfh1 family of homeodomain/zinc finger-containing proteins. Similar to other transcription factors, both Smad-interacting protein-1 (SIP1) and deltaEF1 are capable of repressing E-cadherin transcription through binding to the E2 boxes located in its promoter. In the case of deltaEF1, this repression has been proposed to occur via interaction with the corepressor C-terminal binding protein (CtBP). In this study, we show by coimmunoprecipitation that SIP1 and CtBP interact in vivo and that an isolated CtBP-binding SIP1 fragment depends on CtBP for transcriptional repression. However, and most importantly, full-length SIP1 and deltaEF1 proteins do not depend on their interaction with CtBP to repress transcription from the E-cadherin promoter. Furthermore, in E-cadherin-positive kidney epithelial cells, the conditional synthesis of mutant SIP1 that cannot bind to CtBP abrogates endogenous E-cadherin expression in a similar way as wild-type SIP1. Our results indicate that full-length SIP1 can repress E-cadherin in a CtBP-independent manner.

PMID:
12714599
DOI:
10.1074/jbc.M300597200
[Indexed for MEDLINE]
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