RESUMEN
The DNA damage response kinase ataxia telangiectasia and Rad3-related (ATR) coordinates much of the cellular response to replication stress. The exact mechanisms by which ATR regulates DNA synthesis in conditions of replication stress are largely unknown, but this activity is critical for the viability and proliferation of cancer cells, making ATR a potential therapeutic target. Here we use selective ATR inhibitors to demonstrate that acute inhibition of ATR kinase activity yields rapid cell lethality, disrupts the timing of replication initiation, slows replication elongation, and induces fork collapse. We define the mechanism of this fork collapse, which includes SLX4-dependent cleavage yielding double-strand breaks and CtIP-dependent resection generating excess single-stranded template and nascent DNA strands. Our data suggest that the DNA substrates of these nucleases are generated at least in part by the SMARCAL1 DNA translocase. Properly regulated SMARCAL1 promotes stalled fork repair and restart; however, unregulated SMARCAL1 contributes to fork collapse when ATR is inactivated in both mammalian and Xenopus systems. ATR phosphorylates SMARCAL1 on S652, thereby limiting its fork regression activities and preventing aberrant fork processing. Thus, phosphorylation of SMARCAL1 is one mechanism by which ATR prevents fork collapse, promotes the completion of DNA replication, and maintains genome integrity.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , ADN Helicasas/metabolismo , Replicación del ADN/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Animales , Proteínas de la Ataxia Telangiectasia Mutada , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Daño del ADN/efectos de los fármacos , ADN Helicasas/genética , Replicación del ADN/efectos de los fármacos , ADN de Cadena Simple/genética , Activación Enzimática , Humanos , Fosforilación/efectos de los fármacos , Unión Proteica , Inhibidores de Proteínas Quinasas/farmacología , XenopusAsunto(s)
Antineoplásicos/uso terapéutico , Dasatinib/uso terapéutico , Reordenamiento Génico , Leucemia-Linfoma Linfoblástico de Células T Precursoras/tratamiento farmacológico , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/genética , Niño , Humanos , Masculino , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patología , Pronóstico , Inducción de RemisiónRESUMEN
Radiation-induced lung disease is a known complication of therapeutic lung irradiation, but the features have not been well described in children. We report the clinical, radiologic and histologic features of interstitial lung disease (ILD) in a 4-year-old child who had previously received lung irradiation as part of successful treatment for metastatic Wilms tumor. Her radiologic abnormalities and clinical symptoms developed in an indolent manner. Clinical improvement gradually occurred with corticosteroid therapy. However, the observed radiologic progression from interstitial and reticulonodular opacities to diffuse cystic lung disease, with subsequent improvement, is striking and has not been previously described in children.