CRISPR is the bacterial immune system in which the bacteria is able to integrate the viral DNA in its genome, and then use it against that specific virus when the bacteria is attacked. This specific immune system is conformed of the guide RNA (gRNA), integrated from the virus, and a protein called Cas9. The gRNA is the DNA which was integrated from the virus, and it will direct the CRISPR immune system to the viral DNA. Cas9 then undergoes a conformational change upon gRNA binding that shifts the molecule from an inactive, non-DNA binding conformation, into an active DNA-binding conformation. When Cas9 is active, it will cleave the viral DNA, and basically kill the virus.
Francisco Mojica, from University of Alicante, first discovered CRISPR as immune system of bacteria. It is clear for me that Francisco Mojica will receive a Nobel price in the oncoming future. In 2007, Philippe Horvath revealed the mechanism of action of CRISPR. In 2010, Sylvain Moineau from University of Labal showed that Cas9 cleaves DNA. In 2011, Virginijus Siksnys from Vilnus University demonstrated CRISPR systems can function heterologously in other species. Then in 2013 Feng Zhang and Jennifer Doudna used CRISPR-Cas9 for genome editing purposes. Today, most of these people are involved in a war over the patent.
Applications are endless; disease modeling, agriculture, gene therapy, pharmaceutical, etc. We will cover some of them in future posts.