Cas9 protein

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Cas9 (CRISPR associated protein 9) is a family of endonucleases that cuts DNA at specific sites. The Cas9 proteins are shown to only function as a complex with two types of RNA: CRISPR-RNA (crRNA) and trans-activating CRISPR-RNA (tracrRNA)[1]. Both RNAs are required to guide the Cas9 proteins to specific cleaving sites on double stranded DNA.

In prokaryotes such as S. pyogenes, the CRISPR-Cas9 system works as a defence mechanism to detect and cleave foreign DNAs that may come from plasmids or bacteriophages[2]. CRISPR-Cas9 can be applied in genetic engineering. Cas9 is shown to be useful in bacterial gene manipulation[3]. In human cells, Cas9 can be used to knockout or edit genes with the use of custom guide RNAs (gRNA)[4]. Cas9 proteins can be engineered to have higher levels of specificity when they target desired DNA sequences[5].

References

  1. Jinek M, Chylinski K, Fonfara I, Hauer M, Doudna JA, Charpentier E. A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science. 2012 Aug 17;337(6096):816-21. doi: 10.1126/science.1225829
  2. Jinek M, Chylinski K, Fonfara I, Hauer M, Doudna JA, Charpentier E. A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science. 2012 Aug 17;337(6096):816-21. doi: 10.1126/science.1225829
  3. Jiang W, Bikard D, Cox D, Zhang F, Marraffini LA. RNA-guided editing of bacterial genomes using CRISPR-Cas systems. Nat Biotechnol. 2013 Mar;31(3):233-9. doi: 10.1038/nbt.2508
  4. Mali P, Yang L, Esvelt KM, Aach J, Guell M, DiCarlo JE, et al. RNA-guided human genome engineering via Cas9. Science. 2013 Feb 15;339(6121):823-6. doi: 10.1126/science.1232033
  5. Slaymaker IM, Gao L, Zetsche B, Scott DA, Yan WX, Zhang F. Rationally engineered Cas9 nucleases with improved specificity. Science. 2016 Jan 1;351(6268):84-8. doi: 10.1126/science.aad5227
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