Prime editing is a genome-editing technique that uses reverse transcription to install precise genetic modifications. To identify cellular factors that enhance prime editing, researchers performed genome-scale CRISPR-interference screens and developed scalable prime editing reporters. They identified the small RNA-binding protein La as the strongest mediator of prime editing, which promotes editing across various approaches, edit types, endogenous loci, and cell types. La interacts with the 3′ ends of polyuridylated prime editing guide RNAs (pegRNAs) and epegRNAs, and fusing La's RNA-binding domain to a prime editor protein (PE7) significantly improved prime editing efficiency. PE7 outperformed the standard prime editor (PE2) in multiple conditions, including in primary human cells, and showed promise for disease-related applications. The study provides insights into the cellular processes that affect prime editing and suggests strategies for optimizing this genome-editing tool.Prime editing is a genome-editing technique that uses reverse transcription to install precise genetic modifications. To identify cellular factors that enhance prime editing, researchers performed genome-scale CRISPR-interference screens and developed scalable prime editing reporters. They identified the small RNA-binding protein La as the strongest mediator of prime editing, which promotes editing across various approaches, edit types, endogenous loci, and cell types. La interacts with the 3′ ends of polyuridylated prime editing guide RNAs (pegRNAs) and epegRNAs, and fusing La's RNA-binding domain to a prime editor protein (PE7) significantly improved prime editing efficiency. PE7 outperformed the standard prime editor (PE2) in multiple conditions, including in primary human cells, and showed promise for disease-related applications. The study provides insights into the cellular processes that affect prime editing and suggests strategies for optimizing this genome-editing tool.