Figure 4.

DNA break-induced transition between DNA segregation and intermingling plays an essential role in the process of homology-dependent repair of the break. (A) Newly replicated portions of sister chromosomes because of a topological exclusion spontaneously segregate from each other and take positions preparing them for the ensuing cell division. (B) After dsDNA break, the linear portions flanking the break are free to invade other topological domains including the one with the homologous sequences in the sister chromosome. (C) RecA-mediated homologous pairing leads to rejoining of the two broken ends. (D) After circular nature of the DNA is re-established, the action of topoisomerase IV helps to remove possible interlinks between re-established topological domain and other topological domains.