Journal of Nucleic Acids [27] I. M. Ward, K. Minn, and J. Chen, “UV-induced ataxia- telangiectasia-mutated and Rad3-related (ATR) activation requires replication stress,” Journal of Biological Chemistry, vol. 279, no. 11, pp. 9677–9680, 2004. [28] B. Mukherjee, C. Kessinger, J. Kobayashi et al., “DNA- PK phosphorylates histone H2AX during apoptotic DNA fragmentation in mammalian cells,” DNA Repair, vol. 5, no. 5, pp. 575–590, 2006. [29] T. Reitsema, D. Klokov, J. P. Bana´th, and P. L. Olive, “DNA-PK is responsible for enhanced phosphorylation of histone H2AX under hypertonic conditions,” DNA Repair, vol. 4, no. 10, pp. 1172–1181, 2005. [30] H. Wang, M. Wang, H. Wang, W. Bo¨cker, and G. Iliakis, “Com- plex H2AX phosphorylation patterns by multiple kinases including ATM and DNA-PK in human cells exposed to ionizing radiation and treated with kinase inhibitors,” Journal of Cellular Physiology, vol. 202, no. 2, pp. 492–502, 2005. [31] N. Ayoub, A. D. Jeyasekharan, J. A. Bernal, and A. R. Venki- taraman, “HP1-β mobilization promotes chromatin changes that initiate the DNA damage response,” Nature, vol. 453, no. 7195, pp. 682–686, 2008. [32] A. A. Goodarzi, A. T. Noon, D. Deckbar et al., “ATM signaling facilitates repair of DNA double-strand breaks associated with heterochromatin,” Molecular Cell, vol. 31, no. 2, pp. 167–177, 2008. [33] A. A. Goodarzi, A. T. Noon, and P. A. Jeggo, “The impact of heterochromatin on DSB repair,” Biochemical Society Transac- tions, vol. 37, no. 3, pp. 569–576, 2009. [34] M. S. Luijsterburg, C. Dinant, H. Lans et al., “Heterochro- matin protein 1 is recruited to various types of DNA damage,” Journal of Cell Biology, vol. 185, no. 4, pp. 577–586, 2009. [35] C. Dinant and M. S. Luijsterburg, “The emerging role of HP1 in the DNA damage response,” Molecular and Cellular Biology, vol. 29, no. 24, pp. 6335–6340, 2009. [36] T. T. Paull, E. P. Rogakou, V. Yamazaki, C. U. Kirchgessner, M. Gellert, and W. M. Bonner, “A critical role for histone H2AX in recruitment of repair factors to nuclear foci after DNA damage,” Current Biology, vol. 10, no. 15, pp. 886–895, 2000. [37] J. Kobayashi, H. Tauchi, S. Sakamoto et al., “NBS1 localizes to γ-H2AX foci through interaction with the FHA/BRCT domain,” Current Biology, vol. 12, no. 21, pp. 1846–1851, 2002. [38] J. Kobayashi, A. Antoccia, H. Tauchi, S. Matsuura, and K. Komatsu, “NBS1 and its functional role in the DNA damage response,” DNA Repair, vol. 3, no. 8-9, pp. 855–861, 2004. [39] G. S. Stewart, B. Wang, C. R. Bigneli, A. M. R. Taylor, and S. J. Elledge, “MDC1 is a mediator of the mammalian DNA damage checkpoint,” Nature, vol. 421, no. 6926, pp. 961–966, 2003. [40] M. Stucki and S. P. Jackson, “γH2AX and MDC1: anchoring the DNA-damage-response machinery to broken chromo- somes,” DNA Repair, vol. 5, no. 5, pp. 534–543, 2006. [41] I. M. Ward, K. Minn, K. G. Jorda, and J. Chen, “Accumulation of checkpoint protein 53BP1 at DNA breaks involves its bind- ing to phosphorylated histone H2AX,” Journal of Biological Chemistry, vol. 278, no. 22, pp. 19579–19582, 2003. [42] L. B. Schultz, N. H. Chehab, A. Malikzay, and T. D. Hala- zonetis, “p53 binding protein 1 (53BP1) is an early participant in the cellular response to DNA double-strand breaks,” Journal of Cell Biology, vol. 151, no. 7, pp. 1381–1390, 2000. [43] M. Stucki, J. A. Clapperton, D. Mohammad, M. B. Yaﬀe, S. J. Smerdon, and S. P. Jackson, “MDC1 directly binds 7 phosphorylated histone H2AX to regulate cellular responses to DNA double-strand breaks,” Cell, vol. 123, no. 7, pp. 1213– 1226, 2005. [44] Z. Lou, K. Minter-Dykhouse, S. Franco et al., “MDC1 main- tains genomic stability by participating in the ampliﬁcation of ATM-dependent DNA damage signals,” Molecular Cell, vol. 21, no. 2, pp. 187–200, 2006. [45] A. Celeste, S. Petersen, P. J. Romanienko et al., “Genomic instability in mice lacking histone H2AX,” Science, vol. 296, no. 5569, pp. 922–927, 2002. [46] K. Minter-Dykhouse, I. Ward, M. S. Y. Huen, J. Chen, and Z. Lou, “Distinct versus overlapping functions of MDC1 and 53BP1 in DNA damage response and tumorigenesis,” Journal of Cell Biology, vol. 181, no. 5, pp. 727–735, 2008. [47] T. Kouzarides, “Chromatin modiﬁcations and their function,” Cell, vol. 128, no. 4, pp. 693–705, 2007. [48] S. D. Taverna, H. Li, A. J. Ruthenburg, C. D. Allis, and D. J. Patel, “How chromatin-binding modules interpret histone modiﬁcations: lessons from professional pocket pickers,” Nature Structural and Molecular Biology, vol. 14, no. 11, pp. 1025–1040, 2007. [49] D. Durocher, J. Henckel, A. R. Fersht, and S. P. Jackson, “The FHA domain is a modular phosphopeptide recognition motif,” Molecular Cell, vol. 4, no. 3, pp. 387–394, 1999. [50] I. A. Manke, D. M. Lowery, A. Nguyen, and M. B. Yaﬀe, “BRCT repeats as phosphopeptide-binding modules involved in protein targeting,” Science, vol. 302, no. 5645, pp. 636–639, 2003. [51] X. Yu, C. C. S. Chini, M. He, G. Mer, and J. Chen, “The BRCT domain is a phospho-protein binding domain,” Science, vol. 302, no. 5645, pp. 639–642, 2003. [52] J. A. Clapperton, I. A. Manke, D. M. Lowery et al., “Structure and mechanism of BRCA1 BRCT domain recognition of phosphorylated BACH1 with implications for cancer,” Nature Structural and Molecular Biology, vol. 11, no. 6, pp. 512–518, 2004. [53] R. S. Williams, M. S. Lee, D. D. Hau, and J. N. M. Glover, “Structural basis of phosphopeptide recognition by the BRCT domain of BRCA1,” Nature Structural and Molecular Biology, vol. 11, no. 6, pp. 519–525, 2004. [54] C. Lukas, F. Melander, M. Stucki et al., “Mdc1 couples DNA double-strand break recognition by Nbs1 with its H2AX- dependent chromatin retention,” EMBO Journal, vol. 23, no. 13, pp. 2674–2683, 2004. [55] M. Rodriguez, X. Yu, J. Chen, and Z. Songyang, “Phosphopep- tide Binding Speciﬁcities of BRCA1 COOH-terminal (BRCT) Domains,” Journal of Biological Chemistry, vol. 278, no. 52, pp. 52914–52918, 2003. [56] M. Goldberg, M. Stucki, J. Falck et al., “MDC1 is required for the intra-S-phase DNA damage checkpoint,” Nature, vol. 421, no. 6926, pp. 952–956, 2003. [57] J. Falck, J. Coates, and S. P. Jackson, “Conserved modes of recruitment of ATM, ATR and DNA-PKcs to sites of DNA damage,” Nature, vol. 434, no. 7033, pp. 605–611, 2005. [58] Z. You, C. Chahwan, J. Bailis, T. Hunter, and P. Russell, “ATM activation and its recruitment to damaged DNA require binding to the C terminus of Nbs1,” Molecular and Cellular Biology, vol. 25, no. 13, pp. 5363–5379, 2005. [59] J. R. Chapman and S. P. Jackson, “Phospho-dependent interactions between NBS1 and MDC1 mediate chromatin retention of the MRN complex at sites of DNA damage,” EMBO Reports, vol. 9, no. 8, pp. 795–801, 2008.