Homeobox protein TGIF1 is a protein that, in humans, is encoded by the TGIF1 gene. [5] [6] [7] Alternative splicing has been observed at this locus and eight variants, encoding four distinct isoforms, are described.
The protein encoded by this gene is a member of the three-amino acid loop extension (TALE) superclass of atypical homeodomains. TALE homeobox proteins are highly conserved transcription regulators. This particular homeodomain binds to a previously characterized retinoid X receptor responsive element from the cellular retinol-binding protein II promoter. In addition to its role in inhibiting 9-cis-retinoic acid-dependent RXR alpha transcription activation of the retinoic acid responsive element, the protein is an active transcriptional co-repressor of SMAD2 and may participate in the transmission of nuclear signals during development and in the adult.
Mutations in this gene are associated with holoprosencephaly type 4, which is a structural anomaly of the brain. [7] It has also been associated with risk of otitis media (inflammation of the middle ear)
Homeobox protein TGIF1 has been shown to interact with: