About the Project
Treatment of cells with radiation leads to a range of DNA lesions, including double-strand breaks (DSBs), which are arguably the most dangerous form of DNA damage. Unsurprisingly, therefore, cells possess robust responses to the presence of DNA DSBs that result in the detection, signalling and repair of these lesions. After irradiation, the majority of DNA DSBs are repaired rapidly, but a subset of DSBs (around 15-20%) persists for many hours (Kakarougkas and Jeggo, 2014). Notably, this minority of DSBs are more likely to be repaired inaccurately, and give rise to a disproportionate number of translocations (Barton et al., 2014). Unrepaired or inaccurately repaired DNA DSBs can result in cell lethality, the understanding of which is critical to exploiting these cellular pathways with radiotherapy. Therefore, it is important to understand what is special about the subset of DNA DSBs that make them difficult to repair with rapid kinetics.
In eukaryotes, DNA is compacted by association with histones to form chromatin. There is evidence to suggest that slowly repaired DNA DSBs may be those that are located within heterochromatic structures (Murray et al., 2012). However, there is also evidence that supports the notion that these DSBs did not necessarily arise in pre-existing heterochromatin (Janssen et al., 2016), but rather that heterochromatin proteins are mobilised to these DSBs (Gursoy-Yuzugullu et al., 2016). To address this question, in this project we will make use of a recently developed protocol for mapping DNA breaks using next generation sequencing (Canela et al., 2016). Building on this, we will investigate the contribution of epigenetic regulators to the location and timing of DNA DSB repair following irradiation.
References
Barton, O., Naumann, S. C., Diemer-Biehs, R., Kunzel, J., Steinlage, M., Conrad, S., Makharashvili, N., Wang, J., Feng, L., Lopez, B. S., Paull, T. T., Chen, J., Jeggo, P. A. & Lobrich, M. 2014. Polo-Like Kinase 3 Regulates Ctip During Dna Double-Strand Break Repair In G1. J Cell Biol, 206, 877-94.
Canela, A., Sridharan, S., Sciascia, N., Tubbs, A., Meltzer, P., Sleckman, B. P. & Nussenzweig, A. 2016. Dna Breaks And End Resection Measured Genome-Wide By End Sequencing. Mol Cell, 63, 898-911.
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Gursoy-Yuzugullu, O., House, N. & Price, B. D. 2016. Patching Broken Dna: Nucleosome Dynamics And The Repair Of Dna Breaks. J Mol Biol, 428, 1846-60.
Janssen, A., Breuer, G. A., Brinkman, E. K., Van Der Meulen, A. I., Borden, S. V., Van Steensel, B., Bindra, R. S., Larocque, J. R. & Karpen, G. H. 2016. A Single Double-Strand Break System Reveals Repair Dynamics And Mechanisms In Heterochromatin And Euchromatin. Genes Dev, 30, 1645-57.
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Kakarougkas, A. & Jeggo, P. A. 2014. Dna Dsb Repair Pathway Choice: An Orchestrated Handover Mechanism. Br J Radiol, 87, 20130685.
Karagiannis, T. C. & El-Osta, A. 2006. Modulation Of Cellular Radiation Responses By Histone Deacetylase Inhibitors. Oncogene, 25, 3885-93.
Murray, J. M., Stiff, T. & Jeggo, P. A. 2012. Dna Double-Strand Break Repair Within Heterochromatic Regions. Biochem Soc Trans, 40, 173-8.
Pfister, S. X., Ahrabi, S., Zalmas, L. P., Sarkar, S., Aymard, F., Bachrati, C. Z., Helleday, T., Legube, G., La Thangue, N. B., Porter, A. C. & Humphrey, T. C. 2014. Setd2-Dependent Histone H3k36 Trimethylation Is Required For Homologous Recombination Repair And Genome Stability. Cell Rep, 7, 2006-18.