Clustered regularly interspaced short palindromic repeats (CRISPRs) are derived from DNA fragments of bacteriophages that infect prokaryotes. When infected, the bacteria
capture snips of DNA from the invading virus
to create CRISPR arrays. During subsequent infections, the bacteria produce RNA segments from the CRISPR arrays to target the virus' DNA. CRISPR-associated protein 9 (Cas9) is RNA-guided, binds DNA, and is a cleaving enzyme that functions as an integral component of the bacterial CRISPR adaptive immune system that targets the virus' DNA to disable it (1). To check for sites complementary to the 20 base pair spacer region of the guide RNA (gRNA) of the CRISPR, Cas9 unwinds foreign DNA that invades the bacteria. If the DNA substrate is complementary to the gRNA, Cas9 cleaves the invading DNA, rendering the virus disabled. The presence of a 5'-NGG-3' protospacer adjacent motif (PAM) sequence immediately downstream of the target DNA (protospacer) is required for Cas9 cleavage of foreign DNA. As PAM is absent in bacterial CRISPR loci, cleavage of the host genome is avoided and provides a novel sequence for identification of foreign DNA by Cas9.
technology, double-stranded DNA breaks may be induced within specific targeted genome sequences (target DNA; protospacer) for insertion or removal of DNA sequences for gene editing
applications. To target a specific loci, a gRNA that will bind to a specific target sequence of DNA within a genome is created. The gRNA will recognize the DNA sequence, and the Cas9 enzyme will cleave the DNA at the targeted location. Once the targeted DNA is removed by Cas9, the cell's own DNA repair
mechanism is used to insert or remove a DNA sequence for genomic editing.
Cas9 detection is used to confirm and evaluate CRISPR Cas9 gRNA transfection efficiency. Western blot
analysis of CRISPR-Cas9 gRNA transfected cell lysates with Cas9 antibodies identifies the protein having a theoretical molecular weight of 160kDa. Broad areas of research are benefiting from CRISPR-Cas9 based gene editing tools including studies of basic immunity functions, genetic screening and disease treatment (2). Ethical concerns have led to many countries making it illegal to manipulate human germline cells or perform embryo genome editing.
1. Oakes, B. L., Fellmann, C., Rishi, H., Taylor, K. L., Ren, S. M., Nadler, D. C., . . . Savage, D. F. (2019). CRISPR-Cas9 Circular Permutants as Programmable Scaffolds for Genome Modification. Cell, 176(1-2), 254-267.e216. doi:10.1016/j.cell.2018.11.052
2. Chiou, S. H., Winters, I. P., Wang, J., Naranjo, S., Dudgeon, C., Tamburini, F. B., . . . Winslow, M. M. (2015). Pancreatic cancer modeling using retrograde viral vector delivery and in vivo CRISPR/Cas9-mediated somatic genome editing. Genes Dev, 29(14), 1576-1585. doi:10.1101/gad.264861.115
|Product By Gene ID
- CRISPR-associated protein 9 nuclease