The CRISPR/Cas9 anti-phage immunity system in Streptococcus pyogenes deploys a variety of crRNAs derived from the spacer
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The CRISPR/Cas9 anti-phage immunity system in Streptococcus pyogenes deploys a variety of crRNAs derived from the spacer and repeat sequences in the CRISPR array in the S. pyogenes genome. In combination with the transactivating RNA (tracrRNA), these crRNAs guide the Cas9 endonuclease to complementary sequences in infecting phage genomes, whereupon Cas9 cleaves the phage DNA. A requirement for cleavage is that the targeted phage DNA sequence be immediately upstream of a protospacer adjacent motif (PAM), which in the S. pyogenes system is 5′-NGG-3′. Why is it important that the CRISPR array in the S. pyogenes genome not contain this PAM?
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Principles of Genetics
ISBN: 978-1119142287
7th edition
Authors: D. Peter Snustad, Michael J. Simmons
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