TONSOKU reads the histone H3.1 variant to mediate DNA repair during replication

The histone H3.1 variant is specifically inserted on chromatin during DNA replication in eukaryotes. A single amino acid variation (position 31) in the N-terminal tail of H3.1 compared to replication-independent H3.3 is conserved in plants and animals, but no function has been assigned to amino acid 31 to justify a role for H3.1 during replication. In this study, we demonstrate that the protein TONSOKU (TSK/TONSL), which participates in rescuing broken replication forks, specifically interacts with H3.1 via recognition of alanine 31 by its tetratricopeptide repeat (TPR) domain. We show that genomic amplification in the absence of H3K27me1 in plants depends on H3.1, TSK and DNA polymerase theta (Pol ?). Overall, our study reveals similar strategies in plants and animals for regulating TSK activity and post-replicative chromatin maturation, with both clades using the H3.1 variant and different histone mono-methyltransferases (ATXR5/ATXR6 or SET8) to achieve this. Overall design: Examination of RNA seq in 4 different backgrounds col0, atxr5/6, tsk. atxr5/6 tsk and DNA sequencing in 6 different backgrounds (col0, atxr5/6, tsk. atxr5/6 tsk, polq and atxr5/6 polq )