Deciphering the chromatin landscape induced around DNA double strand breaks.

DNA double strand breaks (DSBs) are among the most deleterious forms of lesions and deciphering the details of the chromatin landscape induced around DSBs represents a great challenge for molecular biologists. Chromatin Immunoprecipitation, followed by microarray hybridisation (ChIP-chip) or high-throughput sequencing (ChIP-seq), are powerful techniques that provide high-resolution maps of protein-genome interactions. However, applying these techniques to study chromatin changes induced around DSBs was previously hindered due to a lack of suitable DSB induction techniques. We have recently developed an experimental system utilizing a restriction enzyme fused to a modified oestrogen receptor ligand binding domain (AsiSI-ER), which generates multiple, sequence-specific and unambiguously positioned DSBs across the genome upon induction with 4-hydroxytamoxifen (4OHT).(1) Cell lines expressing this construct represent a powerful tool to study specific chromatin changes during DSB repair, enabling high-resolution profiling of DNA repair complexes and chromatin modifications induced around DSBs. Using this system, we have recently produced the first map of gammaH2AX, a DSB-induced chromatin modification, on two human chromosomes and have investigated its spreading properties.(1) Here we provide additional data characterizing the cell lines, present a genome-wide profile of gammaH2AX obtained by ChIP-seq, and discuss the potential of our system towards investigations of previously uncharacterized aspects of DSB repair.