FIG. 3.

The PU.1 kb −14 URE includes two highly homologous regions conserved in five mammalian species. (A) The diagram (not drawn to scale) represents the two homologous regions, which are separated by a 425-bp “spacer” in which there is no significant sequence similarity. The location of a major SFFV integration site is shown within this spacer. The two homologous regions and spacer lie centrally within the 3.4-kb HindIII fragment at kb −14 utilized in the transgenic constructs (Fig. 1). Bp 1 at the 5′ end of the distal homology region is 14,505 bp 5′ of the transcription start site (GenBank accession number AL691450) (9). (B) Sequence alignment of the kb −14 murine PU.1 URE with rat, human, dog, and rabbit PU.1 genomic sequences. Identical residues are shown in black. The PU.1 binding site identified by ChIP and EMSA analysis in Fig. 4 and 5 is enclosed in a bracket.