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XB-ART-16408
EMBO J 1997 Jun 16;1612:3644-54. doi: 10.1093/emboj/16.12.3644.
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Functional dissection of a transcriptionally active, target-specific Hox-Pbx complex.

Di Rocco G , Mavilio F , Zappavigna V .


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Hox genes control cell fates and specify regional identities in vertebrate development. Hox proteins show a relaxed DNA-binding selectivity in vitro, suggesting that functional specificity is achieved in vivo through the action of transcriptional co-factors. Pbx proteins are good candidates for such a role, on the basis of both genetic and biochemical evidence. We report that the human Pbx1 and HOXB1 proteins can cooperatively activate transcription through a genetically characterized Hox target, i.e. an autoregulatory element directing spatially restricted expression of the murine Hoxb-1 gene (b1-ARE) in the developing hindbrain. On the b1-ARE, only a restricted subset of HOX proteins (HOXA1, HOXB1, HOXA2) are able to bind cooperatively with Pbx1 and activate transcription. Selective recognition of the b1-ARE is mediated by the N-terminal region of the HOX homeodomain. The DNA-binding and protein-protein interaction functions of HOXB1 and Pbx1 are all necessary for the assembly of a transcriptionally active complex on the b1-ARE. Functional dissection of the complex allowed the localization of the main activation domain in the HOXB1 N-terminal region, and of an additional one in the C-terminal region of Pbx1 contained in the Pbx1a but not in the alternatively spliced Pbx1b isoform. Our results indicate that Pbx1 acts as a transcriptional co-factor of Hox proteins, allowing selective recognition and cooperative activation of regulatory target sequences.

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Species referenced: Xenopus
Genes referenced: hoxb1 pbx1

References [+] :
Arcioni, The upstream region of the human homeobox gene HOX3D is a target for regulation by retinoic acid and HOX homeoproteins. 1992, Pubmed