Identification of CRISPR RNA processing. (a) The crRNA sequencing reads were mapped to the two N. equitans CRISPR clusters to determine the abundance of individual crRNAs. Processing occurs within the repeat elements, generating crRNAs with a 5'-terminal ATTGAAAG 8 nucleotide tag (underlined) and gradual trimming of the 3'-terminal tag. Arrows indicate hotspots for trimming. (b) Sequencing reads upstream of the first repeat within the identical leader sequence of both CRISPR arrays indicate the transcription start site (+1) and a potential promoter TATA box (box A) element.
Randau Genome Biology 2012 13:R63 doi:10.1186/gb-2012-13-7-r63