Enhanced chromatin dynamics by FACT promotes transcriptional restart after UV-induced DNA damage.

Chromatin remodeling is tightly linked to all DNA-transacting activities. To study chromatin remodeling during DNA repair, we established quantitative fluorescence imaging methods to measure the exchange of histones in chromatin in living cells. We show that particularly H2A and H2B are evicted and replaced at an accelerated pace at sites of UV-induced DNA damage. This accelerated exchange of H2A/H2B is facilitated by SPT16, one of the two subunits of the histone chaperone FACT (facilitates chromatin transcription) but largely independent of its partner SSRP1. Interestingly, SPT16 is targeted to sites of UV light-induced DNA damage-arrested transcription and is required for efficient restart of RNA synthesis upon damage removal. Together, our data uncover an important role for chromatin dynamics at the crossroads of transcription and the UV-induced DNA damage response.