DNA double-strand breaks (DSBs) are among the most deleterious forms of DNA lesions in cells. Here we induced site-specific DSBs in yeast cells and monitored chromatin dynamics surrounding the DSB using Chromosome Conformation Capture (3C). We find that formation of a DSB within G1 cells is not sufficient to alter chromosome dynamics. However, DSBs formed within an asynchronous cell population result in large decreases in both intraand interchromosomal interactions. Using live cell microscopy, we find that changes in chromosome dynamics correlate with relocalization of the DSB to the nuclear periphery. Sequestration to the periphery requires the nuclear envelope protein, Mps3p, and Mps3p-dependent tethering delays recombinational repair of a DSB and enhances gross chromosomal rearrangements. Furthermore, we show that components of the telomerase machinery are recruited to a DSB and that telomerase recruitment is required for its peripheral localization. Based on these findings, we propose that sequestration of unrepaired or slowly repaired DSBs to the nuclear periphery reflects a competition between alternative repair pathways.[Keywords: Chromatin; DNA double-strand break; DNA repair; Mps3p; Rad52; 3C] Supplemental material is available at http://www.genesdev.org.

E fficient repair of DNA double strand breaks is essential for cells to avoid increased mutation rates, genomic instability, and even cell death. Consequently, cells have evolved multiple mechanisms for rapidly repairing these DNA lesions, including error-free homologous recombination as well as error-prone pathways such as nonhomologous end joining. What happens to DSBs that are repaired inefficiently or not at all? Recently, several studies in budding yeast have shown that these more recalcitrant DSBs are localized to the nuclear periphery through interactions between the nuclear envelope protein, Mps3, and proteins associated with DSB chromatin. Why these DSBs are tethered to the nuclear periphery is still not clear, though the current view is that alternative repair pathways may be activated at the periphery in a final attempt to repair the lesion. In this Extra View, we discuss these recent reports, and we show that the Est1 component of the telomerase machinery plays an essential role in anchoring DSB chromatin to the nuclear envelope protein, Mps3.

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