CRISPR In Brief

CRISPR is a natural process that occurs within the bacteria's adaptive immune system, as one of the many defense mechanisms used by bacteria to protect against genetic invaders. Bacteria identify and store fragments of DNA from invading viruses. When the cell recognizes a new viral attack, it uses this stored DNA signature to synthetize the related RNA molecule, which works as a guide in tandem with Cas9, an endonuclease from the bacterium Streptococcus pyogenes, to make double-stranded cuts in the DNA of the bacteria-invading virus to disable it. The DNA signature, which contains repeating sequences of genetic code, interrupted by spacer sequences of genetic code from previous viral attacks, are called clustered regulatory interspaced short palindromic repeats, or CRISPR. The transition from this natural process in bacteria to potential human therapeutic use was enabled by the discovery of a second RNA strand in guiding Cas9 to make the cuts in the DNA. (Also see "Can CRISPR Make The Jump To Therapeutics?" - Scrip, 20 March, 2014.)