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di Rocco, G.* ; Gavalas, A.* ; Popperl, H.* ; Krumlauf, R.* ; Mavilio, F.* ; Zappavigna, V.*

The recruitment of SOX/OCT complexes and the differential activity of HOXA1 and HOXB1 modulate the Hoxb1 auto-regulatory enhancer function.

J. Biol. Chem. 276, 20506-20515 (2001)
DOI PMC
Open Access Gold as soon as Publ. Version/Full Text is submitted to ZB.
Regionally restricted expression patterns of Hox genes in developing embryos rely on auto-, cross-, and para-regulatory transcriptional elements. One example is the Hoxb1 auto-regulatory element (b1-ARE), which drives expression of Hoxb1 in the fourth rhombomere of the hindbrain. We previously showed that HOXB1 and PBX1 activate transcription from the b1-ARE by binding to sequences required for the expression of a reporter gene in rhombomere 4 in vivo. We now report that in embryonal carcinoma cells, which retain characteristics of primitive neuroectodermal cells, the b1-ARE displays higher basal and HOX/PBX-induced activities than in other cell backgrounds. We have identified a bipartite-binding site for SOX/OCT heterodimers within the b1-ARE that accounts for its cell context-specific activity and is required for maximal transcriptional activity of HOX/PBX complexes in embryonal carcinoma cells. Furthermore, we found that in an embryonal carcinoma cell background, HOXB1 has a significantly higher transcriptional activity than its paralog HOXA1. We map the determinants for this differential activity within the HOXB1 N-terminal transcriptional activation domain. By using analysis in transgenic and HOXA1 mutant mice, we extended these findings on the differential activities of HOXA1 and HOXB1 in vivo, and we demonstrated that they are important for regulating aspects of HOXB1 expression in the hindbrain. We found that mutation of the SOX/OCT site and targeted inactivation of Hoxa1 both impair the response of the b1-ARE to retinoic acid in transgenic mice. Our results show that Hoxa1 is the primary mediator of the response of b1-ARE to retinoic acid in vivo and that this function is dependent on the binding of SOX/OCT heterodimers to the b1-ARE. These results uncover novel functional differences between Hox paralogs and their modulators.
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Publication type Article: Journal article
Document type Scientific Article
Language english
Publication Year 2001
HGF-reported in Year 0
ISSN (print) / ISBN 0021-9258
e-ISSN 1083-351X
Quellenangaben Volume: 276, Issue: 23, Pages: 20506-20515 Article Number: , Supplement: ,
Publisher American Society for Biochemistry and Molecular Biology
Reviewing status Peer reviewed
Institute(s) Institute of Pancreatic Islet Research (IPI)
POF-Topic(s) 90000 - German Center for Diabetes Research
Research field(s) Helmholtz Diabetes Center
PSP Element(s) G-502600-003
PubMed ID 11278854
Erfassungsdatum 2001-12-31