REVIEW Chromatin Modifications and DNA Double-Strand Breaks
Leukemia (2007) 21, 195–200 & 2007 Nature Publishing Group All rights reserved 0887-6924/07 $30.00 www.nature.com/leu REVIEW Chromatin modifications and DNA double-strand breaks: the current state of play TC Karagiannis1,2 and A El-Osta3 1Molecular Radiation Biology, Trescowthick Research Laboratories, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia; 2Department of Pathology, The University of Melbourne, Parkville, Melbourne, Victoria, Australia and 3Epigenetics in Human Health and Disease, Baker Medical Research Institute, The Alfred Medical Research and Education Precinct, Prahran, Victoria, Australia The packaging and compaction of DNA into chromatin is mutated (ATM) and ataxia telangiectasia-related (also known as important for all DNA-metabolism processes such as transcrip- Rad3-related, ATR), which are members of the phosphoinositide tion, replication and repair. The involvement of chromatin 4,5 modifications in transcriptional regulation is relatively well 3-kinase (PI(3)K) superfamily. They catalyse the phosphoryla- characterized, and the distinct patterns of chromatin transitions tion of numerous downstream substrates that are involved in 4,5 that guide the process are thought to be the result of a code on cell-cycle regulation, DNA repair and apoptosis. the histone proteins (histone code). In contrast to transcription, In mammalian cells, DSBs are repaired by one of two distinct the intricate link between chromatin and responses to DNA and complementary pathways – homologous recombination damage has been given attention only recently. It is now (HR) and non-homologous end-joining (NHEJ).6,7 Briefly, NHEJ emerging that specific ATP-dependent chromatin remodeling involves processing of the broken DNA terminii to make them complexes (including the Ino80, Swi/Snf and RSC remodelers) 3 and certain constitutive (methylation of lysine 79 of histone H3) compatible, followed by a ligation step.
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