title: TSC loss distorts DNA replication programme and sensitises cells to genotoxic stress.
abstract: Tuberous Sclerosis (TSC) is characterized by exorbitant mTORC1 signalling and manifests as non-malignant, apoptosis-prone neoplasia. Previous reports have shown that TSC-/- cells are highly susceptible to mild, innocuous doses of genotoxic stress, which drive TSC-/- cells into apoptotic death. It has been argued that this hypersensitivity to stress derives from a metabolic/energetic shortfall in TSC-/- cells, but how metabolic dysregulation affects the DNA damage response and cell cycle alterations in TSC-/- cells exposed to genotoxic stress is not understood. We report here the occurrence of futile checkpoint responses and an unusual type of replicative stress (RS) in TSC1-/- fibroblasts exposed to low-dose genotoxins. This RS is characterized by elevated nucleotide incorporation rates despite only modest origin over-firing. Strikingly, an increased propensity for asymmetric fork progression and profuse chromosomal aberrations upon mild DNA damage confirmed that TSC loss indeed proved detrimental to stress adaptation. We conclude that low stress tolerance of TSC-/- cells manifests at the level of DNA replication control, imposing strong negative selection on genomic instability that could in turn detain TSC-mutant tumours benign.
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, University Hospital, 07745 Jena, Germany.
authors.forename: Govind M
authors.initials: GM
authors.lastname: Pai
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, Department of Radiotherapy and Radiooncology, Center of Oncology, University Medical Center Hamburg-Eppendorf, Germany, 20246 Hamburg, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Zielinski
authors.affiliation: Leibniz Institute on Aging - Fritz Lipmann Institute, 07745 Jena, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Koalick
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, University Hospital, 07745 Jena, Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Ludwig
authors.affiliation: Leibniz Institute on Aging - Fritz Lipmann Institute, 07745 Jena, Germany.
authors.forename: Zhao-Qi
authors.initials: ZQ
authors.lastname: Wang
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, Department of Radiotherapy and Radiooncology, Center of Oncology, University Medical Center Hamburg-Eppendorf, Germany, 20246 Hamburg, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Borgmann
authors.affiliation: Leibniz Institute on Aging - Fritz Lipmann Institute, 07745 Jena, Germany.|Faculty of Biochemistry and Molecular Medicine, University of Oulu, 90014 Oulu, Finland.
authors.forename: Helmut
authors.initials: H
authors.lastname: Pospiech
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, University Hospital, 07745 Jena, Germany.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Rubio
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000139:chemically induced; D004249:DNA Damage; D004261:DNA Replication; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D042822:Genomic Instability / Q000187:drug effects; D006918:Hydroxyurea / Q000633:toxicity*; D018345:Mice, Knockout; D034622:RNA Interference; D020123:Sirolimus / Q000633:toxicity*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000172:deficiency* / Q000235:genetics
chemical_list: C000624651:Tsc1 protein, mouse; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D004317:Doxorubicin; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus; D006918:Hydroxyurea
keywords: adaptive responses; genotoxic stress; mTORC1; replication stress; tuberous sclerosis