Figure 4.

Closely similar DNase I footprints of pol III in transcriptionally competent and inactive promoter complexes. TFIIIB, containing TBPm₃ and full length B′′ or B′′Δ372–387, and pol III were bound to a 132-bp DNA probe containing the TGTA variant of the SNR6 promoter. Two-dimensional DNase I protection analysis (see Methods) yielded the aligned and normalized phosphorimage profiles of DNase I cleavage that are displayed. (Part of the bp −51 to −61 segment that was used for normalization is not shown.) (a) Top line: Footprints of the TFIIIB[B′′Δ372–387]-DNA and TFIIIB-DNA complexes showing regions of reduced (█) and enhanced (▨) cleavage caused by TFIIIB. (b) Comparison of the DNase I cleavage profiles of the pol III–TFIIIB–DNA complex () and TFIIIB–DNA complex (⋯ ·) formed with B′′Δ372–387. Protection () and enhanced cleavage ( ) attributable to pol III binding are marked below the panel. (c) Comparison as in b but for complexes assembled with full length B′′.