The ins and outs of heterochromatic DNA repair

Abstract

Repetitive DNA is often packaged into heterochromatin structures that prevent illicit recombination events that cause genomic instability. A recent study by Chiolo et al. (2011) published in Cell finds that DNA double-strand breaks formed within heterochromatin are shuttled to adjacent sites that are "safe" to complete repair by recombination.

Figure 1. Model for re-localization of DSBs induced in a heterochromatic domain

Initial DSB recognition and processing occurs within heterochromatin (left). The Smc5/6 SUMO ligase complex could then inhibit recruitment of the Rad51 recombinase. This allows DSB processing to induce heterochromatin expansion and DSB mobilization to a euchromatic site where the DSB is trapped outside the heterochromatin domain for completion of repair (right).