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Publication Abstract from PubMed

Wnt signaling activates target genes by promoting association of the co-activator beta-catenin with TCF/LEF transcription factors. In the absence of beta-catenin, target genes are silenced by TCF-mediated recruitment of TLE/Groucho proteins, but the molecular basis for TLE/TCF-dependent repression is unclear. We describe the unusual three-dimensional structure of the N-terminal Q domain of TLE1 that mediates tetramerization and binds to TCFs. We find that differences in repression potential of TCF/LEFs correlates with their affinities for TLE-Q, rather than direct competition between beta-catenin and TLE for TCFs as part of an activation-repression switch. Structure-based mutation of the TLE tetramer interface shows that dimers cannot mediate repression, even though they bind to TCFs with the same affinity as tetramers. Furthermore, the TLE Q tetramer, not the dimer, binds to chromatin, specifically to K20 methylated histone H4 tails, suggesting that the TCF/TLE tetramer complex promotes structural transitions of chromatin to mediate repression.

Molecular functions of the TLE tetramerization domain in Wnt target gene repression.,Chodaparambil JV, Pate KT, Hepler MR, Tsai BP, Muthurajan UM, Luger K, Waterman ML, Weis WI EMBO J. 2014 Apr 1;33(7):719-31. doi: 10.1002/embj.201387188. Epub 2014 Mar 3. PMID:24596249^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.