Prime editing system

MIT and Harvard researchers have developed a new means of CRISPR gene editing that they believe could correct most of the genetic mutations that cause disease.  It is called “prime editing,” and it works like this: “First, the [prime editing guide] RNA guides the prime editor to the desired section of the genome. There, instead of cutting both strands of DNA, the Cas9 enzyme nicks just one strand. The pegRNA also contains a sequence of letters that will be inserted into the genome – the RT [ reverse transcriptase] protein reads that sequence and writes the corresponding DNA letters to the end of the nicked piece of DNA. It can do this by converting individual DNA letters into others.  Next, the cell itself will naturally cut out the original, unwanted DNA sequence, and seal the new letters into the genome. But that creates a mismatch between the two strands – one half of the DNA sequence will be edited and the other won’t be. To fix that, another guide RNA will then direct the prime editor to nick the unedited strand. That small “injury” tells the cell to repair the strand, and it will do so by copying the edited strand.”      MORE

Image Credit: The Harvard Gazette