In vivo Protein-DNA Interactions at the β-Globin Gene Locus

We have investigated in vivo protein-DNA interactions in the beta-globin gene locus by dimethyl sulfate (DMS) footprinting in K562 cells, which express epsilon- and gamma-globin but not beta-globin. In the locus control region, hypersensitive site 2 (HS-2) exhibited footprints in several putative protein binding motifs. HS-3 was not footprinted. The beta promoter was also not footprinted, while extensive footprints were observed in the promoter of the active gamma-globin gene. No footprints were seen in the A gamma and beta 3' enhancers. With several motifs, additional protein interactions and alterations in binding patterns occurred with hemin induction. In HeLa cells, some footprints were observed in some of the motifs in HS-2, compatible with the finding that HS-2 has some enhancer function in HeLa cells, albeit much weaker than its activity in K562 cells. No footprint was seen in B lymphocytes. In vivo footprinting is a useful method for studying relevant protein-DNA interactions in erythroid cells.