Xenbase Image ID: 129318

Figure 2. CRISPR-mediated regulation of gene expression in Francisella novicida(a) Genetic organization of the type II-B CRISPR-Cas system present in F. novicida. It contains 14 different spacer sequences and cas4 instead of csn2. Unique to this system is the presence of a small CRISPR-Cas-associated RNA (scaRNA) transcribed in the same orientation as the CRISPR array. (b) Trans-activating CRISPR RNA (tracrRNA):scaRNA-mediated gene repression. The 5′ end of the tracrRNA is homologous to the repeat sequences (yellow line). This allows its interaction with the scaRNA and its incorporation within Cas9. The 3′ end of the tracrRNA has homology to the bacterial lipoprotein (BLP) messenger RNA and directs the degradation/cleavage of this transcript by an unknown mechanism. Abbreviations: cas, CRISPR-associated; CRISPR, clustered regularly interspaced short palindromic repeats. Image published in: Bikard D and Marraffini LA (2013) © 2013 Faculty of 1000 Ltd. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license Larger Image Printer Friendly View

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