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. 2010 Jul;1(7):787–796. doi: 10.1177/1947601910382774

Figure 2.

Figure 2.

Double-strand break–induced (DSB-induced) transcriptional silencing. (A) Schematic of the transcription reporter locus. The lac operator (256 copies) is followed by the tetracycline response element (96 repeats) and a CMV promoter-driven reporter gene that codes for the CFP-SKL protein and the MS2 RNA stem loop (24 repeats). Expression of the mCherry-Lac repressor-FokI nuclease domain fusion protein induces DSBs within the lac operator region. Transcription of the report gene can be induced by doxycycline and visualized by YFP-MS2 that binds to the MS2 stem loops. (B) DSB-induced local transcriptional silencing. DSBs induce the synthesis of histone H2A ubiquitin and K63-linked polyubiquitin chains at sites of damage. Although histone H2A ubiquitin is responsible for DSB-induced ATM-dependent transcriptional silencing, K63-linked polyubiquitin chains are responsible for the recruitment of repair factors.