Damage in transition.
Double-stranded DNA breaks (DSBs) are a particularly dangerous form of DNA damage because they can lead to chromosome loss, translocations or truncations. When DSBs occur, many proteins are recruited to the break site; these proteins serve to both initiate DNA repair and to activate a checkpoint response. Repair occurs via one of two pathways: non-homologous end-joining (NHEJ), in which broken DNA ends are directly ligated; or homologous recombination (HR), in which a homologous chromosome is used as a template in a replicative repair process. The checkpoint response is mediated by the phosphatidyl inositol 3-kinase-like kinases, Mec1 and Tel1 (ATR and ATM in humans, respectively). Two recent studies in yeast have significantly increased our understanding of when each of the proteins involved in these processes is localized to a break and, in addition, how their sequential localization is achieved. Specifically, these studies support and expand upon a model in which Tel1 and the NHEJ proteins are the first proteins to localize to the break to initiate signaling and attempt repair, but are subsequently replaced by Mec1 and the HR proteins. This transition is mediated by a cyclin-dependent kinase-dependent initiation of 5'-->3' processing (resection) of the DSB. Thus, the cell-cycle stage at which DSBs occur affects the way in which the DSBs are processed and recognized.
Garber
Peter M
PM
Cancer Research Institute, Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94115, USA.
Vidanes
Genevieve M
GM
Toczyski
David P
DP
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins / Q000502:physiology; D018844:Cyclin-Dependent Kinases / Q000502:physiology; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D005656:Fungal Proteins / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008957:Models, Genetic; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011995:Recombination, Genetic; D051716:Replication Protein A; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology; D025521:Tumor Suppressor Proteins / Q000502:physiology
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C513623:TEL1 protein, S cerevisiae; D018844:Cyclin-Dependent Kinases