FLICKR, CAROLINE DAVISCRISPR/Cas9, now widely used as a precise way to edit DNA, involves the Cas9 protein locating pre-programmed sequences of base pairs before slicing and dicing the genome. Two recent reports, one published in Nature (October 28) and the other in Science (November 12), unveil details about how Cas9 ensures it targets the right sequences.
In the Science paper, CRISPR pioneer Jennifer Doudna from the University of California, Berkley, and her colleagues explored how the Cas9 protein searches for a single pattern of base pairs in an entire genome. Cas9 operates in conjunction with an RNA, programmed to guide Cas9 to a specific 20-nucleotide section of DNA. “It’s crazy that the Cas9 complex manages to scan the vast space of eukaryotic genomes,” study coauthor Spencer Knight of Berkeley said in a press release.
The team visualized Cas9’s binding patterns with single-particle tracking, finding that once the protein recognizes a primer sequence in the DNA, it will bind to incorrect areas that look like its actual target—but Cas9 tends to disengage from these mistakes in less than a second. These steps ...
