Example of an ancient gBGC-induced mUCE. (A) A 380-bp mUCE.1304 is located in the intergenic region close to PAX2 and shows ultraconservation in eutherians and birds. (B) Alignment of mUCE.1304 shows that a gBGC event occurred in the eutherian ancestor and perfectly maintained ultraconservation during mammalian evolution. (C) Specific alignment of the 143-bp subregion. Dots in the sequence alignment refer to bases that are identical to those in the avian genome. (D) Specific changes in predicted transcription factor binding motifs owing to gBGC-induced alterations within the 143-bp subregion. The corresponding motif locations were shown in C. (E) Dual-luciferase reporter gene assay for the assessment of mUCE.1304 enhancer activity. Relative luciferase activity of reporter vectors containing mUCE (human ortholog of mUCE.1304) and aUCE (chicken ortholog of mUCE.1304) was measured in the human embryonic kidney 293T cell line (left) and chicken embryonic fibroblast DF-1 cell line (right). Six replications were performed for each experimental group. (****) P-value < 0.0001.
