(A) Schematic illustration of modified promoters (also see Fig. S2). The wild type SNR20 promoter, the SNR20 promoter with a C+4G mutation introduced in the TSS (SNR20 91W), and the SNR20 promoter with deletions (indicated by dashed lines) bringing the +1 TSS to positions 29, 31, and 33 bp from the TATA box (SNR20 29D, SNR20 31D, SNR20 33D). (B) Run-off transcription with the modified SNR20 promoters. For reactions with the inhibitor-sensitive mutant TFIIK-L83G, 1.1 mM NA-PP1 was added.