Location of ribosomal RNA processing sites. (A) shows an annotated view of the rrnA cluster. Labelling indicates the position of TSSs (p1 and p2) and major processing sites referred to in the text. The position of p1 is just downstream of a processing site associated with upstream transcription, which is detectable using a narrower range of reads. Short horizontal, filled arrows (blue and green) indicate the positions of complementary regions that facilitate extensive base-pairing. The insets show better the position of the promoters at the 5′ end of 16S RNA and cleavages at the very 5′ end of 23S and 5S using a narrower range of reads (following TAP treatment, dRNA-seq+). The remainder of the labelling is as Figure 2. (B) and (C) show the base-pairing of the complementary regions that flank 16S and 23S rRNA, respectively. For each, the positions of staggered cleavages are shown.