Fig. 4. Transcriptional activity of HOXD13, HOXD13(I47L) and HOXD13(IQN) at the HCR. P19 cells were transiently transfected with 10 µg of pTHCR reporter construct and the indicated quantities of expression constructs. Bars represent the mean luciferase activity±s.e.m. of at least six independent experiments. (A) Transcriptional activity mediated by increasing amounts of pSG-HOXD13, pSG-HOXD13(I47L) or pSG-HOXD13(IQN) assayed separately. (B) Transcriptional activity mediated by 1.0 µg pSG-HOXD13 in the presence of increasing amounts of pSG-HOXD13(I47L) or pSG-HOXD13(IQN), with the activity mediated by increasing amounts of pSG-HOXD13 shown for comparison. (C) Sequence of the HCR element, with potential Hox core binding motifs (5'-TAAT-3' or 5'-TTAT-3') on the forward strand and reverse strands over- and underlined respectively. The single 5'-TTAC-3' motif is highlighted in grey.