Figure 3. tracrRNA and pre-crRNA co-processing in selected type II CRISPR-Cas systems. CRISPR loci architectures with verified positions and directions of tracrRNA and pre-crRNA transcription are shown. Black sequences, pre-crRNA repeats; red sequences, tracrRNA sequences base-pairing with crRNA repeats. Putative RNA processing sites as revealed by RNA sequencing are indicated with arrowheads. For each locus, arrowhead sizes represent relative amounts of the retrieved 5′ and 3′-ends (see Table S3). Blue arrowhead pairs represent putative RNase III co-processing sites with dark blue indicating the putative primary processing sites.