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. Author manuscript; available in PMC: 2010 Nov 22.
Published in final edited form as: Genes Cancer. 2010 Jul 1;1(7):787–796. doi: 10.1177/1947601910382774

Figure 2.

Figure 2

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 poly-ubiquitin chains at sites of damage. While histone H2A ubiquitin is responsible for DSB-induced ATM dependent transcriptional silencing, K63-linked poly-ubiquitin chains are responsible for the recruitment of repair factors.