What are the components of a typical prime editor?

Prime editing consists of two main components: a Cas9 nickase fused with a modified reverse transcriptase (known as PE2), and a multifunctional guide RNA called prime editing guide RNA (pegRNA). 

• The Cas9 nickase (nCas9) is a version of the Cas9 enzyme that can create single-strand breaks, or nicks, in the DNA rather than full double-strand breaks. 
• In the prime editing system, a reverse transcriptase is combined with a Cas9 nickase that carries the H840A mutation. Together, the Cas9 nickase and reverse transcriptase facilitate the editing of the DNA sequence by creating nicks and introducing new genetic material at the target site. 
• The pegRNA guides the Cas9 nickase to the correct genomic location and provides the information needed for prime editing to occur, including the desired edit and the sequence of DNA to be synthesized. The Cas9-H840A/pegRNA complex attaches to the specified target area and makes a cut of 3 base pairs before the PAM site.