Interaction between Smad-interacting protein-1 and the corepressor C-terminal binding protein is dispensable for transcriptional repression of E-cadherin.
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.
van Grunsven
Leo A
LA
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.
Michiels
Christine
C
Van de Putte
Tom
T
Nelles
Luc
L
Wuytens
Gunther
G
Verschueren
Kristin
K
Huylebroeck
Danny
D
D000429:Alcohol Oxidoreductases; D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004285:Dogs; D015536:Down-Regulation; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques; D015854:Up-Regulation; D000074165:Zinc Finger E-box Binding Homeobox 2
D015820:Cadherins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D010455:Peptides; D010750:Phosphoproteins; D012097:Repressor Proteins; C492363:ZEB2 protein, human; C120602:ZEB2 protein, mouse; D000074165:Zinc Finger E-box Binding Homeobox 2; D000429:Alcohol Oxidoreductases; C096794:C-terminal binding protein; D008156:Luciferases