Which molecular factor(s) suppress CRISPR-Cas mediated HDR?

CRISPR-Cas mediated homology-directed repair (HDR) allows for precise genome modifications, but achieving high HDR efficiency can be challenging in some cells. By conducting a genome-wide screening in Fanconi anemia patient cell lines, researchers identified TREX1, an exonuclease, as a key factor that reduces HDR efficiency when linear DNA is used as a repair template. High TREX1 levels are linked to poor HDR, making it a biomarker for HDR efficiency. Strategies such as TREX1 removal and chemically protected DNA templates were found to enhance HDR outcomes, offering valuable insights for improving genome editing techniques.