How does prime editing work?

Prime editing is a versatile genome editing technology developed to precisely modify DNA sequences without requiring double-strand breaks. It combines the guide RNA (gRNA) of CRISPR-Cas9 with a modified Cas9 enzyme fused to a reverse transcriptase. 

Prime editing starts by delivering a special guide RNA and a fusion protein into the target cell. Once inside, the fusion protein makes a cut in the cell's DNA at the desired spot, following the instructions from the guide RNA. This begins reverse transcription of the template sequence in the pegRNA. The unedited strand is eliminated, leaving behind the newly edited strand. Subsequently, this edited strand pairs up with its complementary strand to create double-stranded DNA. This creates a mismatch between the edited and unedited DNA strands and can lead to two possibilities. One possibility is that the cell's repair mechanism copies the edited information onto the complementary strand, making the edit permanent in the cell's DNA. Alternatively, the original DNA sequence may be reinserted into the edited strand, reversing the edit in the cell's DNA.