A novel homeobox protein which recognizes a TGT core and functionally interferes with a retinoid-responsive motif.
We describe here a novel homeobox gene, denoted TGIF (5"TG3' interacting factor), which belongs to an expanding TALE (three amino acid loop extension) superclass of atypical homeodomains. The TGIF homeodomain binds to a previously characterized retinoid X receptor (RXR) responsive element from the cellular retinol-binding protein II promoter (CRBPII-RXRE), which contains an unusual DNA target for a homeobox. The interactions of both the homeprotein TGIF and receptor RXR alpha with the CREBPII-RXRE DNA motif occur on overlapping areas and generate a mutually exclusive binding in vitro. Transient cellular transfections demonstrate that TGIF inhibits the 9-cis-retinoic acid-dependent RXR alpha transcription activation of the retinoic acid responsive element. TGIF transcripts were detected in a restricted number of tissues. The canonical binding site of TGIF is conserved and is an integral part of several responsive elements which are organized like the CRBPII-RXRE. Hence, a novel auxiliary factor to the steroid receptor superfamily may participate in the transmission of nuclear signals during development and in the adult, as illustrated by the down-modulation of the RXR alpha activities.
Bertolino
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E
Roche Ltd., Research Laboratories, Basel, Switzerland.
Reimund
B
B
Wildt-Perinic
D
D
Clerc
R G
RG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D012097:Repressor Proteins; D047488:Retinoid X Receptors; D012177:Retinol-Binding Proteins / Q000235:genetics / Q000378:metabolism; D054840:Retinol-Binding Proteins, Cellular; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D018076:DNA, Complementary; D018398:Homeodomain Proteins; C518459:RBP2 protein, human; C518461:Rbp2 protein, rat; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; D047488:Retinoid X Receptors; D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; C097504:TGIF1 protein, human; D014157:Transcription Factors