New study reveals how PARP can limit prime editing-mediated insertions-published in THE CRISPR JOURNAL

Prime editing enables precise modifications to DNA without introducing double-strand breaks, offering exciting opportunities for genome engineering. However, editing efficiency can vary considerably depending on the type of modification and genomic location. What determines these differences, and can they be overcome?

In a new study published in The CRISPR Journal, research assistant Iryna Vykhlyantseva from the Genome Engineering and Measurement Lab (GEML), together with colleagues from the Corn Lab and the Rossi Group  (IUF Düsseldorf), investigated how DNA repair pathways influence prime editing outcomes, identifying PARP1 as an important regulator of insertion efficiency.

By screening 569 compounds targeting DNA damage and repair pathways, we found that inhibiting PARP activity could more than double prime editing-mediated insertions at a specific genomic locus, without a comparable effect on substitutions or deletions. Gene knockout experiments confirmed that PARP1 was primarily responsible for this effect. Importantly, the improvement extended across different prime editing configurations, insertion sizes, and cell types, including primary human T cells, without increasing unwanted editing byproducts.

However, the effect depended on the genomic location and the design of the reverse transcription template, highlighting the importance of cellular and sequence context in determining editing outcomes.

These findings identify PARP1 as a context-dependent barrier to precise DNA insertions and suggest that targeting PARP activity could provide a strategy for improving prime editing-mediated insertions in suitable contexts.

Read the paper in The CRISPR Journal.