Prime editing maps essential histone H3 lysines in mammalian cells
Researchers developed a high-throughput CRISPR prime-editing platform to mutate all canonical histone H3 genes in mouse embryonic stem cells and map lysine requirements for cell fitness. The screen pinpointed key residues (H3K4, H3K9, H3K14, H3K18, H3K79) whose disruption reduces fitness, with H3K56 playing a conserved role in genome stability; combinatorial edits reveal functional crosstalk (for example, H3K27R + H3K36R impairs self-renewal and transcription). The approach can occasionally generate kilobase-scale deletions in histone clusters when nicking is used, but careful screening yields clean clones, establishing a functional map of H3 lysines and a versatile toolkit for studying chromatin regulation in mammals.
