Beyond The Nucleus: Translating Engineered Protein Localization To Chromatin Modifying Enzymes.

Chromatin-modifying enzymes (CMEs) have traditionally been studied in their nuclear context for regulating gene expression. However, recent evidence points to the significant non-canonical functions that they perform in the cytoplasm, mitochondria, and plasma membrane, which can contribute to disease progression and alter cell phenotypes. This review surveys emerging engineering approaches to control protein localization, which could be applied to CMEs, particularly histone-modifying enzymes. Natural regulatory mechanisms include nuclear import/export signals and mechanical force-mediated translocation. Engineering strategies encompass diverse approaches: synthetic localization signals for directional transport, RNA editing systems like SNAP-ADAR, and small molecule platforms including bifunctional compounds, self-localizing ligands, and nanobody-mediated translocation. Optogenetic tools provide spatiotemporal control through light-inducible trapping, while inducible condensates enable reversible protein sequestration. Additional tools provide extra control via protease-based cleavage mechanisms and endogenous secondary messenger coupling. Despite significant advances in protein relocalization technologies, their application to CMEs remains largely unexplored, which would allow us to decode mechanisms of disease and develop targeted therapeutic interventions for those diseases. Future applications of these tools to CMEs will elucidate our understanding of epigenetic regulation and expand how we conceptualize CMEs.