passages.id: split_5_test_1021_passage
passages.type: progene_text
passages.text: This bipartite transcription factor is targeted to the upstream regulatory regions of Tcf target genes including Siamois and Nodal related gene-3 in Xenopus , engrailed and Ultrabithorax in Drosophila via the sequence - specific HMG box , and mediates their transcriptional activation by virtue of transactivation domains contributed by beta-catenin / Armadillo .