Transcriptional repression by Msx-1 does not require homeodomain DNA-binding sites.
This study investigates the transcriptional properties of Msx-1, a murine homeodomain protein which has been proposed to play a key role in regulating the differentiation and/or proliferation state of specific cell populations during embryogenesis. We show, using basal and activated transcription templates, that Msx-1 is a potent repressor of transcription and can function through both TATA-containing and TATA-less promoters. Moreover, repression in vivo and in vitro occurs in the absence of DNA-binding sites for the Msx-1 homeodomain. Utilizing a series of truncated Msx-1 polypeptides, we show that multiple regions of Msx-1 contribute to repression, and these are rich in alanine, glycine, and proline residues. When fused to a heterologous DNA-binding domain, both N- and C-terminal regions of Msx-1 retain repressor function, which is dependent upon the presence of the heterologous DNA-binding site. Moreover, a polypeptide consisting of the full-length Msx-1 fused to a heterologous DNA-binding domain is a more potent repressor than either the N- or C-terminal regions alone, and this fusion retains the ability to repress transcription in the absence of the heterologous DNA site. We further show that Msx-1 represses transcription in vitro in a purified reconstituted assay system and interacts with protein complexes composed of TBP and TFIIA (DA) and TBP, TFIIA, and TFIIB (DAB) in gel retardation assays, suggesting that the mechanism of repression is mediated through interaction(s) with a component(s) of the core transcription complex. We speculate that the repressor function of Msx-1 is critical for its proposed role in embryogenesis as a regulator of cellular differentiation.
Catron
K M
KM
Center for Advanced Biotechnology and Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway.
Zhang
H
H
Marshall
S C
SC
Inostroza
J A
JA
Wilson
J M
JM
Abate
C
C
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004622:Embryo, Mammalian; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D051957:MSX1 Transcription Factor; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D016133:Polymerase Chain Reaction; D017510:Protein Folding; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D013489:Suppression, Genetic; D013698:Templates, Genetic; D014157:Transcription Factors; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D004247:DNA