The plant-specific DDR factor SOG1 increases chromatin mobility in response to DNA damage

Abstract

Homologous recombination (HR) is a conservative DNA repair pathway in which intact homologous sequences are used as a template for repair. How the homology search happens in the crowded space of the cell nucleus is, however, still poorly understood. Here, we measured global chromosome and double-strand break (DSB) site mobility in Arabidopsis thaliana, using lacO/LacI lines and two GFP-tagged HR reporters. We observed an increase in global chromatin mobility upon the induction of DNA damage, specifically at the S/G2 phases of the cell cycle. DSB sites showed remarkably high mobility levels at the early HR stage, with a subsequent drastic decrease in mobility associated with the relocation of DSBs to the nucleus periphery. Importantly, the increase in mobility was lost in sog1-1 mutant, a central transcription factor of the DNA damage response in plants. Our results indicate that repair mechanisms actively regulate chromatin mobility upon DNA damage, implying an important role for this process during the early steps of the DNA damage response.