Figure 1.

Trophoblast cells have a unique transcription start site associated with an additional array of HLA-C-specific TF-binding sites. A. The sequence of the core promoter region of HLA-C*01 is shown, and nucleotides that are polymorphic in other HLA-C alleles are shown in orange type. Only nucleotide differences that are present in all alleles are shown for the HLA-B and HLA-A genes. Predicted TF-binding sites and their consensus sequences are shown in bold above the sequence, and nucleotides that match the consensus are underlined in the HLA-C sequence. The conserved TBP and NF-Y binding sites are indicated by black boxes, whereas sites that vary between genes are shown in blue boxes. Nucleotide differences found in all HLA-A and HLA-B alleles are shown in green type, as is the RFX consensus binding sequence. HLA-C transcription start sites (TSS) mapped by 5´ RACE in BeWo cells are marked by black asterisks. The core TSS found in most tissues is marked by a black asterisk. Previously defined functional elements, Enhancer A, ISRE, X1, X2 and Y sites are labeled. The vertical red lines indicate junctions between the 5´, central, and 3´ regions. B. The sequence of promoter elements and their relative positions is shown for the core and trophoblast-associated TSS. The relative position of the overlapping TF-binding arrays is shown below, with putative trophoblast elements indicated by blue boxes, and core elements shown as green boxes.