The Interaction of the Carboxyl Terminus-binding Protein with the Smad Corepressor TGIF Is Disrupted by a Holoprosencephaly Mutation in TGIF

Abstract

The homeodomain protein TGIF represses transcription in part by recruiting histone deacetylases. TGIF binds directly to DNA to repress transcription or interacts with TGF-β-activated Smads, thereby repressing genes normally activated by TGF-β. Loss of function mutations in TGIF result in holoprosencephaly (HPE) in humans. One HPE mutation in TGIFresults in a single amino acid substitution in a conserved PLDLS motif within the amino-terminal repression domain. We demonstrate that TGIF interacts with the corepressor carboxyl terminus-binding protein (CtBP) via this motif. CtBP, which was first identified by its ability to bind the adenovirus E1A protein, interacts both with gene-specific transcriptional repressors and with a subset of polycomb proteins. Efficient repression of TGF-β-activated gene responses by TGIF is dependent on interaction with CtBP, and we show that TGIF is able to recruit CtBP to a TGF-β-activated Smad complex. Disruption of the PLDLS motif in TGIF abolishes the interaction of CtBP with TGIF and compromises the ability of TGIF to repress transcription. Thus, at least one HPE mutation in TGIF appears to prevent CtBP-dependent transcriptional repression by TGIF, suggesting an important developmental role for the recruitment of CtBP by TGIF. The homeodomain protein TGIF represses transcription in part by recruiting histone deacetylases. TGIF binds directly to DNA to repress transcription or interacts with TGF-β-activated Smads, thereby repressing genes normally activated by TGF-β. Loss of function mutations in TGIF result in holoprosencephaly (HPE) in humans. One HPE mutation in TGIFresults in a single amino acid substitution in a conserved PLDLS motif within the amino-terminal repression domain. We demonstrate that TGIF interacts with the corepressor carboxyl terminus-binding protein (CtBP) via this motif. CtBP, which was first identified by its ability to bind the adenovirus E1A protein, interacts both with gene-specific transcriptional repressors and with a subset of polycomb proteins. Efficient repression of TGF-β-activated gene responses by TGIF is dependent on interaction with CtBP, and we show that TGIF is able to recruit CtBP to a TGF-β-activated Smad complex. Disruption of the PLDLS motif in TGIF abolishes the interaction of CtBP with TGIF and compromises the ability of TGIF to repress transcription. Thus, at least one HPE mutation in TGIF appears to prevent CtBP-dependent transcriptional repression by TGIF, suggesting an important developmental role for the recruitment of CtBP by TGIF. three amino acid loop extension holoprosencephaly Gal4 DNA binding domain histone deacetylase carboxyl terminus-binding protein hemagglutinin polymerase chain reaction polycomb group Homeobox genes were first identified in Drosophilawhere they regulate segment identity. The homeodomain is an approximately 60-amino acid DNA-binding domain consisting of three α-helices, which is conserved among numerous proteins from diverse species (1Gehring W.J. Affolter M. Burglin T. Annu. Rev. Biochem. 1994; 63: 517-526Crossref Scopus (846) Google Scholar, 2McGinnis W. Levine M.S. Hafen E. Kuroiwa A. Gehring W.J. Nature. 1984; 308: 428-433Crossref PubMed Scopus (693) Google Scholar, 3McGinnis W. Garber R.L. Wirz J. Kuroiwa A. Gehring W.J. Cell. 1984; 37: 403-408Abstract Full Text PDF PubMed Scopus (548) Google Scholar). Members of the atypical TALE1 homeodomain family have a three amino acid loopextension between helices one and two of the homeodomain (4Bertolino E. Reimund B. Wildt-Perinic D. Clerc R. J. Biol. Chem. 1995; 270: 31178-31188Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar, 5Burglin T.R. Nucleic Acids Res. 1997; 25: 4173-4180Crossref PubMed Scopus (486) Google Scholar). Despite the similarity of their homeodomains, outside this region TALE proteins are considerably divergent. Members of this family bind to DNA in association with other homeodomain proteins (6Berthelsen J. Zappavigna V. Mavilio F. Blasi F. EMBO J. 1998; 17: 1423-1433Crossref PubMed Scopus (149) Google Scholar, 7Knoepfler P.S. Lu Q. Kamps M.P. Nucleic Acids Res. 1996; 24: 2288-2294Crossref PubMed Scopus (62) Google Scholar, 8Knoepfler P.S. Calvo K.R. Chen H. Antonarakis S.E. Kamps M.P. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 14553-14558Crossref PubMed Scopus (167) Google Scholar, 9Shanmugam K. Green N.C. Rambaldi I. Saragovi H.U. Featherstone M.S. Mol. Cell. Biol. 1999; 19: 7577-7588Crossref PubMed Scopus (130) Google Scholar) and can activate and repress transcription (10Jacobs Y. Schnabel C.A. Cleary M.L. Mol. Cell. Biol. 1999; 19: 5134-5142Crossref PubMed Scopus (212) Google Scholar, 11Berthelsen J. Zappavigna V. Ferretti E. Mavilio F. Blasi F. EMBO J. 1998; 17: 1434-1445Crossref PubMed Scopus (181) Google Scholar, 12Asahara H. Dutta S. Kao H.Y. Evans R.M. Montminy M. Mol. Cell. Biol. 1999; 19: 8219-8225Crossref PubMed Scopus (129) Google Scholar).The TALE homeodomain protein TGIF (TG-interacting factor) was identified by its ability to bind a specific retinoid responsive element and has been suggested to compete with retinoid receptors for binding to this element (4Bertolino E. Reimund B. Wildt-Perinic D. Clerc R. J. Biol. Chem. 1995; 270: 31178-31188Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar, 13Bertolino E. Wildt S. Richards G. Clerc R.G. Dev. Dyn. 1996; 205: 410-420Crossref PubMed Scopus (42) Google Scholar). However, it is not clear what role TGIF plays in the regulation of retinoid-responsive transcription. TGIF can also bind to an element within the upstream of the D1Adopamine receptor gene and is able to compete for binding with Meis2, another TALE family homeodomain protein (14Yang Y. Hwang C.K. D'Souza U.M. Lee S.H. Junn E. Mouradian M.M. J. Biol. Chem. 2000; 275: 20734-20741Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). TGIF is a transcriptional repressor that contains multiple repression domains and interacts with histone deacetylases (HDAC) (15Wotton D. Lo R.S. Lee S. Massague J. Cell. 1999; 97: 29-39Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar, 16Wotton D. Lo R.S. Swaby L.A. Massague J. J. Biol. Chem. 1999; 274: 37105-37110Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar). Transcriptional repression by TGIF is dependent only in part on its ability to recruit HDACs, and TGIF contains at least one HDAC-independent transcriptional repression domain (16Wotton D. Lo R.S. Swaby L.A. Massague J. J. Biol. Chem. 1999; 274: 37105-37110Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar).The transcriptional response to transforming growth factor TGF-β is dependent on the intracellular mediators of TGF-β signaling, the Smad proteins. Following TGF-β receptor-mediated phosphorylation and activation, the activated Smad complex moves to the J. A. F. Biol. 1997; Full Text PDF PubMed Scopus Google Scholar, K. Nature. 1997; PubMed Scopus Google Scholar, Y. R. Biol. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar, J. D. EMBO J. 2000; 19: PubMed Google Scholar). Smad complex is to specific DNA via with other DNA-binding proteins M. Nature. 1996; PubMed Scopus Google Scholar, Dev. 1998; PubMed Scopus Google Scholar) and by S. B. S.E. Mol. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. H. J. Cell. 1998; 94: Full Text Full Text PDF PubMed Scopus Google Scholar, J. K. Chen S. A. Nature. 1997; PubMed Scopus Google Scholar). by in dependent on with Y. R. Dev. 1998; PubMed Scopus Google Scholar, R. T. Dev. 1998; PubMed Scopus Google Scholar, J. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, Mol. Biol. Cell. 1998; PubMed Scopus Google Scholar). TGF-β-activated Smad complex can also with TGIF, in transcriptional repression by TGIF is dependent on with for interaction with the and on the repression of TGIF (15Wotton D. Lo R.S. Lee S. Massague J. Cell. 1999; 97: 29-39Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar). appears that both and repression domains of TGIF a role in repression of a TGF-β or mutation of a single of the which to the holoprosencephaly a of D. E. A. Massague J. M. 2000; 25: PubMed Scopus Google Scholar, M. 1998; PubMed Scopus Google Scholar, J. K. M. J. 1995; Google Scholar). The in HPE of of the and are by is not clear mutations result in HPE of on the TGF-β or on repression of other gene was first identified a protein which binds the carboxyl of the E1A protein U. S. E. T. G. Proc. Natl. Acad. Sci. U. S. A. 1995; PubMed Scopus Google Scholar, T. U. M. S. G. EMBO J. PubMed Scopus Google and this interaction is for transcriptional repression by the acid was to for interaction with CtBP U. S. E. T. G. Proc. Natl. Acad. Sci. U. S. A. 1995; PubMed Scopus Google Scholar). motif to is in other transcriptional repressors that bind CtBP J. M. EMBO J. 1998; 17: PubMed Scopus Google Scholar, Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, T. H. H. Y. Mol. Cell. Biol. 1999; 19: PubMed Google Scholar, Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar). has that within a subset of proteins bind CtBP R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). CtBP not only with gene-specific repressors also with of transcriptional repression demonstrate that CtBP and TGIF via a PLDLS motif in the amino-terminal repression domain of TGIF. response to TGIF can recruit CtBP to an activated Smad complex. The interaction of TGIF with CtBP is for repression by TGIF and is by a single amino acid which in is a transcriptional repressor with multiple repression which appears to in a (15Wotton D. Lo R.S. Lee S. Massague J. Cell. 1999; 97: 29-39Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar, 16Wotton D. Lo R.S. Swaby L.A. Massague J. J. Biol. Chem. 1999; 274: 37105-37110Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar). TGIF represses transcription to DNA via its or to DNA by with TGF-β-activated by the of TGIF is dependent on the ability of the repression domain of TGIF to recruit We show that the amino-terminal repression domain of TGIF, which represses transcription of interacts with the interaction is dependent on the of a conserved motif within TGIF amino have been identified in transcriptional repressors and have been to for recruitment of CtBP J. M. EMBO J. 1998; 17: PubMed Scopus Google Scholar). this motif is conserved in of TGIF from other the protein and TGIF. of TGIF not to in or protein with a homeodomain is that this protein bind to the DNA function from it to TGIF repression with transcriptional CtBP is able to with a subset of polycomb group proteins via a motif within proteins R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). proteins in are which a role in the repression of gene V. R. Dev. 1995; PubMed Scopus Google Scholar, M. J. 1995; 17: PubMed Scopus Google Scholar). complex of proteins is in its of transcriptional repression is not clear J. A. M. J. Mol. Biol. 1997; PubMed Scopus Google Scholar, M. E. A. A. M. Dev. 1997; PubMed Scopus Google Scholar, J. D. P.S. J. Biol. 1998; PubMed Scopus Google Scholar). CtBP is able to with the and R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google this the that a of CtBP an interaction between a gene-specific repressor and a complex of transcriptional repressors has suggested that CtBP represses via an HDAC-independent J. K. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar). we show that TGIF is able to with both CtBP and suggesting that TGIF able to recruit both of transcriptional repressors to a specific the that TGIF part of a complex of transcriptional which to to specific DNA via DNA binding or by interaction with TGF-β-activated However, we the that corepressor of TGIF with CtBP in the of CtBP a TGF-β-activated Smad suggesting that TGIF can recruit both and CtBP to a Smad complex in response to TGF-β or is also that this result in the recruitment of proteins to an activated Smad complex. of to the of the corepressor complex which TGIF is able to to TGF-β-activated Despite the that and CtBP can with TGIF it is that TGIF only one of corepressor to a specific of of transcriptional repression a role at or at the However, it appears that at least for repression of gene responses by TGIF, both the CtBP and interaction domains are to the ability of the amino of TGIF to recruit CtBP, it is that this region of the protein represses transcription by a homeodomain proteins have been to repress transcription via with transcription Transcriptional repression by and is by of the homeodomain with the protein Mol. Cell. Biol. 1998; PubMed Scopus Google Scholar, H. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google and repression by with T. 1997; PubMed Scopus Google Scholar). of the PLDLS motif in TGIF interaction with CtBP have only a on transcriptional repression by the amino-terminal of the the homeodomain appears not to interaction with CtBP transcriptional Thus, it is that the TGIF homeodomain represses transcription by a via with transcription or mutation of a single of TGIF in in HPE D. E. A. Massague J. M. 2000; 25: PubMed Scopus Google Scholar). One identified mutation in TGIF in a single amino acid within the PLDLS which we show interaction with appears that of the interaction between TGIF and CtBP can have a on in humans. it to mutations HPE by TGF-β gene responses or by repression of of we demonstrate that TGIF interacts with CtBP via a conserved motif within the amino-terminal repression domain of TGIF and that the of this motif is both for interaction with CtBP and for transcriptional repression by TGIF. The of this interaction is by the that an HPE mutation the PLDLS motif in TGIF and the interaction with Homeobox genes were first identified in Drosophilawhere they regulate segment identity. The homeodomain is an approximately 60-amino acid DNA-binding domain consisting of three α-helices, which is conserved among numerous proteins from diverse species (1Gehring W.J. Affolter M. Burglin T. Annu. Rev. Biochem. 1994; 63: 517-526Crossref Scopus (846) Google Scholar, 2McGinnis W. Levine M.S. Hafen E. Kuroiwa A. Gehring W.J. Nature. 1984; 308: 428-433Crossref PubMed Scopus (693) Google Scholar, 3McGinnis W. Garber R.L. Wirz J. Kuroiwa A. Gehring W.J. Cell. 1984; 37: 403-408Abstract Full Text PDF PubMed Scopus (548) Google Scholar). Members of the atypical TALE1 homeodomain family have a three amino acid loopextension between helices one and two of the homeodomain (4Bertolino E. Reimund B. Wildt-Perinic D. Clerc R. J. Biol. Chem. 1995; 270: 31178-31188Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar, 5Burglin T.R. Nucleic Acids Res. 1997; 25: 4173-4180Crossref PubMed Scopus (486) Google Scholar). Despite the similarity of their homeodomains, outside this region TALE proteins are considerably divergent. Members of this family bind to DNA in association with other homeodomain proteins (6Berthelsen J. Zappavigna V. Mavilio F. Blasi F. EMBO J. 1998; 17: 1423-1433Crossref PubMed Scopus (149) Google Scholar, 7Knoepfler P.S. Lu Q. Kamps M.P. Nucleic Acids Res. 1996; 24: 2288-2294Crossref PubMed Scopus (62) Google Scholar, 8Knoepfler P.S. Calvo K.R. Chen H. Antonarakis S.E. Kamps M.P. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 14553-14558Crossref PubMed Scopus (167) Google Scholar, 9Shanmugam K. Green N.C. Rambaldi I. Saragovi H.U. Featherstone M.S. Mol. Cell. Biol. 1999; 19: 7577-7588Crossref PubMed Scopus (130) Google Scholar) and can activate and repress transcription (10Jacobs Y. Schnabel C.A. Cleary M.L. Mol. Cell. Biol. 1999; 19: 5134-5142Crossref PubMed Scopus (212) Google Scholar, 11Berthelsen J. Zappavigna V. Ferretti E. Mavilio F. Blasi F. EMBO J. 1998; 17: 1434-1445Crossref PubMed Scopus (181) Google Scholar, 12Asahara H. Dutta S. Kao H.Y. Evans R.M. Montminy M. Mol. Cell. Biol. 1999; 19: 8219-8225Crossref PubMed Scopus (129) Google Scholar). The TALE homeodomain protein TGIF (TG-interacting factor) was identified by its ability to bind a specific retinoid responsive element and has been suggested to compete with retinoid receptors for binding to this element (4Bertolino E. Reimund B. Wildt-Perinic D. Clerc R. J. Biol. Chem. 1995; 270: 31178-31188Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar, 13Bertolino E. Wildt S. Richards G. Clerc R.G. Dev. Dyn. 1996; 205: 410-420Crossref PubMed Scopus (42) Google Scholar). However, it is not clear what role TGIF plays in the regulation of retinoid-responsive transcription. TGIF can also bind to an element within the upstream of the D1Adopamine receptor gene and is able to compete for binding with Meis2, another TALE family homeodomain protein (14Yang Y. Hwang C.K. D'Souza U.M. Lee S.H. Junn E. Mouradian M.M. J. Biol. Chem. 2000; 275: 20734-20741Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). TGIF is a transcriptional repressor that contains multiple repression domains and interacts with histone deacetylases (HDAC) (15Wotton D. Lo R.S. Lee S. Massague J. Cell. 1999; 97: 29-39Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar, 16Wotton D. Lo R.S. Swaby L.A. Massague J. J. Biol. Chem. 1999; 274: 37105-37110Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar). Transcriptional repression by TGIF is dependent only in part on its ability to recruit HDACs, and TGIF contains at least one HDAC-independent transcriptional repression domain (16Wotton D. Lo R.S. Swaby L.A. Massague J. J. Biol. Chem. 1999; 274: 37105-37110Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar). The transcriptional response to transforming growth factor TGF-β is dependent on the intracellular mediators of TGF-β signaling, the Smad proteins. Following TGF-β receptor-mediated phosphorylation and activation, the activated Smad complex moves to the J. A. F. Biol. 1997; Full Text PDF PubMed Scopus Google Scholar, K. Nature. 1997; PubMed Scopus Google Scholar, Y. R. Biol. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar, J. D. EMBO J. 2000; 19: PubMed Google Scholar). Smad complex is to specific DNA via with other DNA-binding proteins M. Nature. 1996; PubMed Scopus Google Scholar, Dev. 1998; PubMed Scopus Google Scholar) and by S. B. S.E. Mol. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. H. J. Cell. 1998; 94: Full Text Full Text PDF PubMed Scopus Google Scholar, J. K. Chen S. A. Nature. 1997; PubMed Scopus Google Scholar). by in dependent on with Y. R. Dev. 1998; PubMed Scopus Google Scholar, R. T. Dev. 1998; PubMed Scopus Google Scholar, J. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, Mol. Biol. Cell. 1998; PubMed Scopus Google Scholar). TGF-β-activated Smad complex can also with TGIF, in transcriptional repression by TGIF is dependent on with for interaction with the and on the repression of TGIF (15Wotton D. Lo R.S. Lee S. Massague J. Cell. 1999; 97: 29-39Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar). appears that both and repression domains of TGIF a role in repression of a TGF-β or mutation of a single of the which to the holoprosencephaly a of D. E. A. Massague J. M. 2000; 25: PubMed Scopus Google Scholar, M. 1998; PubMed Scopus Google Scholar, J. K. M. J. 1995; Google Scholar). The in HPE of of the and are by is not clear mutations result in HPE of on the TGF-β or on repression of other gene CtBP was first identified a protein which binds the carboxyl of the E1A protein U. S. E. T. G. Proc. Natl. Acad. Sci. U. S. A. 1995; PubMed Scopus Google Scholar, T. U. M. S. G. EMBO J. PubMed Scopus Google and this interaction is for transcriptional repression by the acid was to for interaction with CtBP U. S. E. T. G. Proc. Natl. Acad. Sci. U. S. A. 1995; PubMed Scopus Google Scholar). motif to is in other transcriptional repressors that bind CtBP J. M. EMBO J. 1998; 17: PubMed Scopus Google Scholar, Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, T. H. H. Y. Mol. Cell. Biol. 1999; 19: PubMed Google Scholar, Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar). has that within a subset of proteins bind CtBP R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). CtBP not only with gene-specific repressors also with of transcriptional repression We demonstrate that CtBP and TGIF via a PLDLS motif in the amino-terminal repression domain of TGIF. response to TGIF can recruit CtBP to an activated Smad complex. The interaction of TGIF with CtBP is for repression by TGIF and is by a single amino acid which in is a transcriptional repressor with multiple repression which appears to in a (15Wotton D. Lo R.S. Lee S. Massague J. Cell. 1999; 97: 29-39Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar, 16Wotton D. Lo R.S. Swaby L.A. Massague J. J. Biol. Chem. 1999; 274: 37105-37110Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar). TGIF represses transcription to DNA via its or to DNA by with TGF-β-activated by the of TGIF is dependent on the ability of the repression domain of TGIF to recruit We show that the amino-terminal repression domain of TGIF, which represses transcription of interacts with the interaction is dependent on the of a conserved motif within TGIF amino have been identified in transcriptional repressors and have been to for recruitment of CtBP J. M. EMBO J. 1998; 17: PubMed Scopus Google Scholar). this motif is conserved in of TGIF from other the protein and TGIF. of TGIF not to in or protein with a homeodomain is that this protein bind to the DNA function from it to TGIF repression with transcriptional CtBP is able to with a subset of polycomb group proteins via a motif within proteins R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). proteins in are which a role in the repression of gene V. R. Dev. 1995; PubMed Scopus Google Scholar, M. J. 1995; 17: PubMed Scopus Google Scholar). complex of proteins is in its of transcriptional repression is not clear J. A. M. J. Mol. Biol. 1997; PubMed Scopus Google Scholar, M. E. A. A. M. Dev. 1997; PubMed Scopus Google Scholar, J. D. P.S. J. Biol. 1998; PubMed Scopus Google Scholar). CtBP is able to with the and R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google this the that a of CtBP an interaction between a gene-specific repressor and a complex of transcriptional repressors has suggested that CtBP represses via an HDAC-independent J. K. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar). we show that TGIF is able to with both CtBP and suggesting that TGIF able to recruit both of transcriptional repressors to a specific the that TGIF part of a complex of transcriptional which to to specific DNA via DNA binding or by interaction with TGF-β-activated However, we the that corepressor of TGIF with CtBP in the of CtBP a TGF-β-activated Smad suggesting that TGIF can recruit both and CtBP to a Smad complex in response to TGF-β or is also that this result in the recruitment of proteins to an activated Smad complex. of to the of the corepressor complex which TGIF is able to to TGF-β-activated Despite the that and CtBP can with TGIF it is that TGIF only one of corepressor to a specific of of transcriptional repression a role at or at the However, it appears that at least for repression of gene responses by TGIF, both the CtBP and interaction domains are to the ability of the amino of TGIF to recruit CtBP, it is that this region of the protein represses transcription by a homeodomain proteins have been to repress transcription via with transcription Transcriptional repression by and is by of the homeodomain with the protein Mol. Cell. Biol. 1998; PubMed Scopus Google Scholar, H. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google and repression by with T. 1997; PubMed Scopus Google Scholar). of the PLDLS motif in TGIF interaction with CtBP have only a on transcriptional repression by the amino-terminal of the the homeodomain appears not to interaction with CtBP transcriptional Thus, it is that the TGIF homeodomain represses transcription by a via with transcription or mutation of a single of TGIF in in HPE D. E. A. Massague J. M. 2000; 25: PubMed Scopus Google Scholar). One identified mutation in TGIF in a single amino acid within the PLDLS which we show interaction with appears that of the interaction between TGIF and CtBP can have a on in humans. it to mutations HPE by TGF-β gene responses or by repression of of we demonstrate that TGIF interacts with CtBP via a conserved motif within the amino-terminal repression domain of TGIF and that the of this motif is both for interaction with CtBP and for transcriptional repression by TGIF. The of this interaction is by the that an HPE mutation the PLDLS motif in TGIF and the interaction with TGIF is a transcriptional repressor with multiple repression which appears to in a (15Wotton D. Lo R.S. Lee S. Massague J. Cell. 1999; 97: 29-39Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar, 16Wotton D. Lo R.S. Swaby L.A. Massague J. J. Biol. Chem. 1999; 274: 37105-37110Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar). TGIF represses transcription to DNA via its or to DNA by with TGF-β-activated by the of TGIF is dependent on the ability of the repression domain of TGIF to recruit We show that the amino-terminal repression domain of TGIF, which represses transcription of interacts with the interaction is dependent on the of a conserved motif within TGIF amino have been identified in transcriptional repressors and have been to for recruitment of CtBP J. M. EMBO J. 1998; 17: PubMed Scopus Google Scholar). this motif is conserved in of TGIF from other the protein and TGIF. of TGIF not to in or protein with a homeodomain is that this protein bind to the DNA function from it to TGIF repression with transcriptional CtBP is able to with a subset of polycomb group proteins via a motif within proteins R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). proteins in are which a role in the repression of gene V. R. Dev. 1995; PubMed Scopus Google Scholar, M. J. 1995; 17: PubMed Scopus Google Scholar). complex of proteins is in its of transcriptional repression is not clear J. A. M. J. Mol. Biol. 1997; PubMed Scopus Google Scholar, M. E. A. A. M. Dev. 1997; PubMed Scopus Google Scholar, J. D. P.S. J. Biol. 1998; PubMed Scopus Google Scholar). CtBP is able to with the and R.G. J. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google this the that a of CtBP an interaction between a gene-specific repressor and a complex of transcriptional repressors proteins. has suggested that CtBP represses via an HDAC-independent J. K. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar). we show that TGIF is able to with both CtBP and suggesting that TGIF able to recruit both of transcriptional repressors to a specific the that TGIF part of a complex of transcriptional which to to specific DNA via DNA binding or by interaction with TGF-β-activated However, we the that corepressor of TGIF with CtBP in the of CtBP a TGF-β-activated Smad suggesting that TGIF can recruit both and CtBP to a Smad complex in response to TGF-β or is also that this result in the recruitment of proteins to an activated Smad complex. of to the of the corepressor complex which TGIF is able to to TGF-β-activated Despite the that and CtBP can with TGIF it is that TGIF only one of corepressor to a specific of of transcriptional repression a role at or at the However, it appears that at least for repression of gene responses by TGIF, both the CtBP and interaction domains are to the ability of the amino of TGIF to recruit CtBP, it is that this region of the protein represses transcription by a homeodomain proteins have been to repress transcription via with transcription Transcriptional repression by and is by of the homeodomain with the protein Mol. Cell. Biol. 1998; PubMed Scopus Google Scholar, H. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google and repression by with T. 1997; PubMed Scopus Google Scholar). of the PLDLS motif in TGIF interaction with CtBP have only a on transcriptional repression by the amino-terminal of the the homeodomain appears not to interaction with CtBP transcriptional Thus, it is that the TGIF homeodomain represses transcription by a via with transcription or mutation of a single of TGIF in in HPE D. E. A. Massague J. M. 2000; 25: PubMed Scopus Google Scholar). One identified mutation in TGIF in a single amino acid within the PLDLS which we show interaction with appears that of the interaction between TGIF and CtBP can have a on in humans. it to mutations HPE by TGF-β gene responses or by repression of of we demonstrate that TGIF interacts with CtBP via a conserved motif within the amino-terminal repression domain of TGIF and that the of this motif is both for interaction with CtBP and for transcriptional repression by TGIF. The of this interaction is by the that an HPE mutation the PLDLS motif in TGIF and the interaction with