title: V(D)J recombination activates a p53-dependent DNA damage checkpoint in scid lymphocyte precursors.
abstract: Double-stranded DNA breaks (DSBs) trigger p53-mediated cell cycle arrest or apoptosis pathways that limit the oncogenic consequences of exposure to genotoxic agents, but p53-mediated responses to DSB generated by normal physiologic events have not been documented. "Broken" V(D)J coding ends accumulate in scid lymphocyte precursors as a consequence of a mutation in DNA-dependent protein kinase (DNA-PK). The ensuing failure to rearrange efficiently antigen receptors arrests lymphoid development. Here we show that scid thymocytes express high levels of p53 protein, attributable to recombinase activating gene (RAG)-dependent generation of DSB adjacent to V, D, and J gene segments. To examine the functional importance of p53 expression in vivo, we bred p53-/- scid mice. The absence of p53 facilitated production of in-frame V(D)Jbeta coding joints and developmental progression of scid thymocytes, in addition to a dramatic accumulation of pro-B cells. All mice developed disseminated pro-B or immature T cell lymphoma/leukemia by 7-12 weeks of age. We present evidence that p53 deficiency prolongs the survival of scid lymphocyte precursors harboring broken V(D)J coding ends, allowing the accumulation of aneuploid cells. These results demonstrate that a p53-mediated DNA damage checkpoint contributes to the immune deficiency characteristic of the scid mutation and limits the oncogenic potential of DSBs generated during V(D)J recombination.
authors.affiliation: Division of Immunology and Cancer, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
authors.forename: C J
authors.initials: CJ
authors.lastname: Guidos
authors.forename: C J
authors.initials: CJ
authors.lastname: Williams
authors.forename: I
authors.initials: I
authors.lastname: Grandal
authors.forename: G
authors.initials: G
authors.lastname: Knowles
authors.forename: M T
authors.initials: MT
authors.lastname: Huang
authors.forename: J S
authors.initials: JS
authors.lastname: Danska
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D001854:Bone Marrow Cells; D002453:Cell Cycle; D002470:Cell Survival; D004249:DNA Damage; D017931:DNA Primers / Q000737:chemistry; D005720:Gamma Rays; D018507:Gene Expression Regulation, Developmental; D015322:Gene Rearrangement, B-Lymphocyte; D015329:Gene Rearrangement, T-Lymphocyte; D016158:Genes, p53; D007942:Leukemia, Experimental / Q000235:genetics*; D008223:Lymphoma / Q000235:genetics / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains; D016513:Mice, SCID / Q000235:genetics*; D008969:Molecular Sequence Data; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics*; D011995:Recombination, Genetic; D013601:T-Lymphocytes / Q000502:physiology*; D013950:Thymus Gland; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency* / Q000502:physiology
chemical_list: D017931:DNA Primers; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016159:Tumor Suppressor Protein p53