Prime editing, a precise genome editing technique, uses reverse transcription of template sequences appended to CRISPR-Cas guide RNAs. To identify cellular factors influencing prime editing, genome-scale CRISPR-interference screens were performed using scalable prime editing reporters. The screens revealed the small RNA-binding protein La as a strong mediator of prime editing, promoting efficiency across various approaches, edit types, and cell types. La functionally interacts with the 3' ends of polyuridylated prime editing guide RNAs (pegRNAs). A prime editor (PE7) fused to La's RNA-binding domain significantly improved editing efficiency. This study provides insights into prime editing mechanisms and strategies for stabilizing exogenous small RNAs.

Jun Yan, Paul Oyler-Castrillo, Purnima Ravisankar, Carl C. Ward, Sébastien Levesque, Yangwode Jing, Danny Simpson, Anqi Zhao, Hui Li, Weihao Yan, Laine Goudy, Ralf Schmidt, Sabrina C. Solley, Luke A. Gilbert, Michelle M. Chan, Daniel E. Bauer, Alexander Marson, Lance R. Parsons, Britt Adamson