Figure 2.

(A) Schema for construction of constrained minicircular DNAs. Linear templates for minicircle production contain the CACGTG sequence phased either 31 or 37 bp from the center of the last intrinsically bent dA tract. Minicircles were produced and labeled as described (7). (B) Lack of affinity differences for oriented prebent DNAs but modestly enhanced affinity for linear DNA templates. Minicircular or linearized probes containing the identical b-HLH-ZIP target sequence (derived from adenovirus major late promoter) were subject to electrophoretic mobility-shift analysis as described (9) using purified Max at concentrations indicated as pmol/10 μl of DNA binding reaction mixture. The upper bands represent protein–DNA complex and the lower bands represent unbound free probe. Evidence of preferential affinity for linear probes can be seen from the enhanced ability of Max to deplete unbound linear probes (lower bands at high Max concentrations).