FIG. 1.
B/Da heterodimers bind multiple sites in Sxlpe. DNase I footprinting assays were done at increasing concentrations of GST-tagged SISB and His6-tagged Da proteins. Numbers indicate B/Da footprinting units. One unit equaled 0.3 pmol (15 nM) of each protein. Panels (left to right) illustrate protection from the distal to the proximal region within the 1.4-kb Sxlpe promoter. Site 6 is not shown. Locations of the 11 regions protected by B/Da are summarized in the schematic. Shading represents estimated relative B/Da binding affinity. High-affinity site 7 is black, moderate-affinity sites are gray, low-affinity sites are striped, and putative weak-binding sites are white. Protection of putative sites 2a and 2b was apparent only at 540 nM B/Da (not shown).