title: Concurrent V(D)J recombination and DNA end instability increase interchromosomal trans-rearrangements in ATM-deficient thymocytes.
abstract: During the CD4(-)CD8(-) (DN) stage of T-cell development, RAG-dependent DNA breaks and V(D)J recombination occur at three T-cell receptor (TCR) loci: TCRβ, TCRγ and TCRδ. During this stage, abnormal trans-rearrangements also take place between TCR loci, occurring at increased frequency in absence of the DNA damage response mediator ataxia telangiectasia mutated (ATM). Here, we use this model of physiologic trans-rearrangement to study factors that predispose to rearrangement and the role of ATM in preventing chromosomal translocations. The frequency of DN thymocytes with DNA damage foci at multiple TCR loci simultaneously is increased 2- to 3-fold in the absence of ATM. However, trans-rearrangement is increased 10 000- to 100 000-fold, indicating that ATM function extends beyond timely resolution of DNA breaks. RAG-mediated synaptic complex formation occurs between recombination signal sequences with unequal 12 and 23 base spacer sequences (12/23 rule). TCR trans-rearrangements violate this rule, as we observed similar frequencies of 12/23 and aberrant 12/12 or 23/23 recombination products. This suggests that trans-rearrangements are not the result of trans-synaptic complex formation, but they are instead because of unstable cis synaptic complexes that form simultaneously at distinct TCR loci. Thus, ATM suppresses trans-rearrangement primarily through stabilization of DNA breaks at TCR loci.
authors.affiliation: Department of Microbiology and Immunology, Graduate Program in Life Sciences, University of Maryland Baltimore, Baltimore, MD 21201, USA. bowense@mail.nih.gov
authors.forename: Steven
authors.initials: S
authors.lastname: Bowen
authors.forename: Darawalee
authors.initials: D
authors.lastname: Wangsa
authors.forename: Thomas
authors.initials: T
authors.lastname: Ried
authors.forename: Ferenc
authors.initials: F
authors.lastname: Livak
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Hodes
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004247:DNA / Q000378:metabolism; D053960:DNA Breaks; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015329:Gene Rearrangement, T-Lymphocyte; D051379:Mice; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology; D060168:Thymocytes / Q000276:immunology*; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D060152:V(D)J Recombination
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D004247:DNA; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases