A role for the Msx-1 homeodomain in transcriptional regulation: residues in the N-terminal arm mediate TATA binding protein interaction and transcriptional repression.

Abstract

In a previous study we showed that the murine homeodomain protein Msx-1 is a potent transcriptional repressor and that this activity is independent of its DNA binding function. The implication of these findings is that repression by Msx-1 is mediated through its association with certain protein factors rather than through its interaction with DNA recognition sites, which prompted investigation of the relevant protein factors. Here we show that Msx-1 interacts directly with the TATA binding protein (TBP) but not with several other general transcription factors. This interaction is mediated by the Msx-1 homeodomain, specifically through residues in the N-terminal arm. These same N-terminal arm residues are required for repression by Msx-1, suggesting a functional relationship between TBP association and transcriptional repression. This is further supported by the observation that addition of excess TBP blocks the repressor action of Msx-1 in in vitro transcription assays. Finally, DNA binding activity is separable from both TBP interaction and repression, which further shows that these other activities of the Msx-1 homeodomain are distinct. Therefore, these findings define a role for the Msx-1 homeodomain, particularly the N-terminal arm residues in protein-protein interaction and transcriptional repression, and implicate a more complex role overall for homeodomains in transcriptional regulation.

Contribution of MSX1 variants to the risk of non-syndromic cleft lip and palate in a Malay population

“…23 Although this variant was predicted to be benign using the Polyphen program, it is located exactly one amino acid after the polyalanine tract of MSX1 at the N-terminal, from nucleotides 29 to 36 (29-AAAATAAA-36). Polyalanine tracts are found in the homeodomain of many transcription factors, 27 and have been shown to be associated with several human disorders. 28 Current evidence suggests that polyalanine tracts function by changing the normal folding, degradation and cytoplasmic aggregation of the mutant proteins.…”

Transcriptional repression by the Msx1 homeoprotein is associated with global redistribution of the H3K27me3 repressive mark to the nuclear periphery

“…Notably, the homeodomain of Msx1 that mediates DNA binding also serves as a protein interaction domain with PRC2 complex. 5,7,47,48 Furthermore, Msx1 and PRC2 are co-localized at regulatory regions of Msx1 target genes, and Msx1 association with PRC2 complexes is necessary for myoblast differentiation and repression of myogenic targets.…”

A novel missense mutation in MSX1 underlies autosomal recessive oligodontia with associated dental anomalies in Pakistani families

“…MSX1 has been shown to interact with distal-less homeobox (DLX) and TATA box binding protein (TBP) (Catron et al 1995;Zhang et al 1996). Both these types of interactions have been shown to be mediated by the homeodomain, specifically amino acids in the N-terminal region.…”

“…The conserved regions among the MSX proteins are the MSX homology regions I, II and III (MHR1 to -III), the extended homeodomain (EHD), and the homeodomain (Davidson 1995). The homeodomain consisting of 60 amino acids numbered 166-225 is subdivided into the N-terminal arm (NT arm) and helices I, II and III, which contribute to protein stability, DNA binding specificity, transcriptional repression and protein interactions (Shang et al 1994;Isaac et al 1995;Zhang et al 1996Zhang et al , 1997. In the MSX1 homeodomain, there are several conserved residues that constitute a consensus sequence, which promotes tertiary structure and mediates DNA binding activity (Scott et al 1989;Laughon 1991;Billeter 1993).…”