Direct recruitment of TONSOKU by the N-terminal tails of histone variants H2A.X and H2A.W coordinates DNA repair.

Histone variants play crucial roles in DNA replication and repair. The plant TONSOKU (TSK) requires histone H3.1 unmethylated at lysine 27 for DNA repair at replication forks, but how TSK is recruited to double-strand break (DSB) sites remains unclear. In this study, we show that the leucine-rich repeat (LRR) domain of TSK recognizes the N-terminal tails of histone variants H2A.X and H2A.W-key for DNA repair in euchromatin and heterochromatin, respectively-but not the H2A.Z variant. A unique motif containing multiple basic and acidic residues (BAR motif) in H2A.Z prevents TSK binding. Moreover, disrupting TSK-H2A.X/W binding impairs TSK-mediated DNA repair. Genetic analyses reveal functional complementation between H2A.X and H2A.W in DNA repair, with the H2A.X N terminus being essential. This study reveals a previously unrecognized, H2A.X/W-dependent mechanism for recruiting the DNA repair protein TSK, highlighting the critical role of their N-terminal tails in plant DNA repair.