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. 2018 May 21;16(4):469–480. doi: 10.1080/15476286.2018.1460994

Figure 3.

Figure 3.

Natural and artificial crRNAs. (a) Apart from the unique spacer sequence, each crRNA present in vivo comprises an eight nucleotide long 5′ handle. In addition, the major crRNA population found in vivo contains a twenty-two-nucleotide long 3′ handle, whereas a minor crRNA population contains a five-nucleotide long 3′ handle. A systematic analysis with independently generated articificial crRNAs (icrRNAs) showed that an icrRNA with a seven nucleotide 5′ handle, the spacer sequence and without the 3′ handle is still active. (b) Cas6 independent crRNA maturation: the crRNA sequence is flanked by tRNA-like structures, so called t-elements. These are recognized by the tRNA processing enzymes RNase Z and RNase P which release the mature icrRNA.