DNA Double-Strand Breaks Induce H2Ax Phosphorylation Domains in a Contact-Dependent Manner

Efficient repair of DNA double-strand breaks (DSBs) requires a coordinated DNA Damage Response (DDR), which includes phosphorylation of histone H2Ax, forming ?H2Ax. This histone modification spreads beyond the DSB into neighboring chromatin, generating a DDR platform that protects against end disassociation and degradation, minimizing chromosomal rearrangements. However, mechanisms that determine the breadth and intensity of ?H2Ax domains remain unclear. Here, we show that chromosomal contacts of a DSB site are the primary determinants for ?H2Ax landscapes. DSBs that disrupt a topological border permit extension of ?H2Ax domains into both adjacent compartments. In contrast, DSBs near a border produce highly asymmetric DDR platforms, with ?H2Ax nearly absent from one broken end. Collectively, our findings lend insights into a basic DNA repair mechanism and how the precise location of a DSB may influence genome integrity. Overall design: Examination of 2 different chromatin modification in 3 cell types Examination of chromatin topology by Hi-C in 3 different types and 3 different conditions