The HMG-box domain

The global fold of the HMG box is well conserved and consists of three a-helices arranged in an L-shape (Fig. 2) [21 28]. The structures of the A and B domain 

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A common feature of the Tcf family members is the presence of a highly conserved sequence-specific DNA-binding region known as the HMG box. Similar DNA-binding domains have been identified in SRY/SOX factors and fungal mating type proteins (Laudet et al., 1993). These three subclasses of HMG box all recognize similar 6-8 bp, AT-rich motifs of the canonical sequence [A/T][A/T]CAA[A/T]GG. 

The HMG (high mobility group) box is a DNA-binding domain found in several transcription factors, that can in some cases bend DNA. Some members of this protein family recognize a unique DNA sequence, whereas others bind to a common DNA conformation. 

L, loading module DH, dehydratase KS, p-ketosynthase KR, ketoreductase MT methyltransferase PS, pyran synthase DHh and KRh are DH and KR-like sequences, together with the FkbH domain, they are involved in the formation of D-lactate starter unit HMG-CS, hydroxy-methyl-glutaryl CoA synthase. Acyl-carrier-protein domains are shown as small filled balls with chain attached by the thiol group. The box shows the HMG-CS pathway for the formation of exocyclic enoate. 

In addition to a potential role of HMGB proteins in nucleosome assembly, it has recently become apparent that many chromatin remodeling complexes either contain, or can associate with, a polypeptide containing an HMG-box homologous to the HMGBl B domain (Table 2). Examples of such complexes include the BAF (a mammalian SWI/SNF related complex [106]) and the Drosophila BRM (brahma)... 

Decoville, M., Giraud-Panis, M.J., Mosrin-Huaman, C., Leng, M., and Locker, D. (2000) HMG boxes of DSPl protein interact with the rel homology domain of transcription factors. Nucleic Acids Res. 28, 454-462. 

Fig. IB Structural organization of the T-cell factor proteins (Tcfs). The DNA-binding HMG box and p-catenin/Armadillo binding domains are highly conserved between family members. Lef-1 contains a unique context-dependent activation domain (CAD), which is required for Lef-1-mediated TCRa enhancer activity. The greatest sequence diversity is present within the C termini, which are often generated via alternative splicing. (Ch, chicken X, Xenopus d, Drosophila).

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