RESUMEN
The SLX4 tumor suppressor is a scaffold that plays a pivotal role in several aspects of genome protection, including homologous recombination, interstrand DNA crosslink repair and the maintenance of common fragile sites and telomeres. Here, we unravel an unexpected direct interaction between SLX4 and the DNA helicase RTEL1, which, until now, were viewed as having independent and antagonistic functions. We identify cancer and Hoyeraal-Hreidarsson syndrome-associated mutations in SLX4 and RTEL1, respectively, that abolish SLX4-RTEL1 complex formation. We show that both proteins are recruited to nascent DNA, tightly co-localize with active RNA pol II, and that SLX4, in complex with RTEL1, promotes FANCD2/RNA pol II co-localization. Importantly, disrupting the SLX4-RTEL1 interaction leads to DNA replication defects in unstressed cells, which are rescued by inhibiting transcription. Our data demonstrate that SLX4 and RTEL1 interact to prevent replication-transcription conflicts and provide evidence that this is independent of the nuclease scaffold function of SLX4.
Asunto(s)
ADN Helicasas/metabolismo , Replicación del ADN , Recombinasas/metabolismo , Transcripción Genética , ADN Helicasas/genética , Disqueratosis Congénita/genética , Proteína del Grupo de Complementación D2 de la Anemia de Fanconi/genética , Proteína del Grupo de Complementación D2 de la Anemia de Fanconi/metabolismo , Retardo del Crecimiento Fetal/genética , Mutación de Línea Germinal , Células HeLa , Humanos , Discapacidad Intelectual/genética , Microcefalia/genética , Recombinasas/genéticaRESUMEN
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
RESUMEN
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
RESUMEN
OBJECTIVE: Pulmonary artery smooth muscle cells (PA-SMCs) in pulmonary arterial hypertension (PAH) show similarities to cancer cells. Due to the growth-suppressive and pro-apoptotic effects of p53 and its inactivation in cancer, we hypothesized that the p53 pathway could be altered in PAH. We therefore explored the involvement of p53 in the monocrotaline (MCT) rat model of pulmonary hypertension (PH) and the pathophysiological consequences of p53 inactivation in response to animal treatment with pifithrin-α (PFT, an inhibitor of p53 activity). METHODS AND RESULTS: PH development was assessed by pulmonary arterial pressure, right ventricular hypertrophy and arterial wall thickness. The effect of MCT and PFT on lung p53 pathway expression was evaluated by western blot. Fourteen days of daily PFT treatment (2.2 mg/kg/day), similar to a single injection of MCT (60 mg/kg), induced PH and aggravated MCT-induced PH. In the first week after MCT administration and prior to PH development, p53, p21 and MDM2 protein levels were significantly reduced; whereas PFT administration effectively altered the protein level of p53 targets. Anti-apoptotic and pro-proliferative effects of PFT were revealed by TUNEL and MTT assays on cultured human PA-SMCs treated with 50 µM PFT. CONCLUSIONS: Pharmacological inactivation of p53 is sufficient to induce PH with a chronic treatment by PFT, an effect related to its anti-apoptotic and pro-proliferative properties. The p53 pathway was down-regulated during the first week in the rat MCT model. These in vivo experiments implicate the p53 pathway at the initiation stages of PH pathogenesis.
Asunto(s)
Hipertensión Pulmonar/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Animales , Apoptosis/efectos de los fármacos , Benzotiazoles/farmacología , Proliferación Celular/efectos de los fármacos , Humanos , Hipertensión Pulmonar/inducido químicamente , Hipertensión Pulmonar/genética , Hipertrofia Ventricular Derecha/metabolismo , Masculino , Monocrotalina/toxicidad , Ratas , Ratas Wistar , Tolueno/análogos & derivados , Tolueno/farmacología , Proteína p53 Supresora de Tumor/genéticaRESUMEN
The telomere structure in the Iberian shrew Sorex granarius is characterized by unique, striking features, with short arms of acrocentric chromosomes carrying extremely long telomeres (up to 300 kb) with interspersed ribosomal DNA (rDNA) repeat blocks. In this work, we investigated the telomere physiology of S. granarius fibroblast cells and found that telomere repeats are transcribed on both strands and that there is no telomere-dependent senescence mechanism. Although telomerase activity is detectable throughout cell culture and appears to act on both short and long telomeres, we also discovered that signatures of a recombinogenic activity are omnipresent, including telomere-sister chromatid exchanges, formation of alternative lengthening of telomeres (ALT)-associated PML-like bodies, production of telomere circles, and a high frequency of telomeres carrying marks of a DNA damage response. Our results suggest that recombination participates in the maintenance of the very long telomeres in normal S. granarius fibroblasts. We discuss the possible interplay between the interspersed telomere and rDNA repeats in the stabilization of the very long telomeres in this organism.
Asunto(s)
Fibroblastos/metabolismo , Recombinación Genética/genética , Musarañas/genética , Homeostasis del Telómero/genética , Telómero/genética , Animales , Células Cultivadas , Cromosomas de los Mamíferos/genética , Cromosomas de los Mamíferos/metabolismo , ADN Ribosómico/genética , Diploidia , Musarañas/metabolismo , Telomerasa/genética , Telomerasa/metabolismo , Telómero/metabolismoRESUMEN
Telomeres are specialized structures found at the end of linear chromosomes. Telomere structure and functions are conserved throughout evolution and are essential for genome stability, preventing chromosome ends from being recognized as damaged DNA and from being fused or degraded by the DNA repair machinery. The structure of telomeres is intrinsically dynamic and affected by multiple processes that impact their length and nucleoprotein composition, thus leading to functional and structural heterogeneity. We review here the most significant facets of telomere metabolism and its dynamics, with an emphasis on human biology.
Asunto(s)
Reparación del ADN/genética , ADN/genética , Telomerasa/genética , Homeostasis del Telómero/genética , Telómero/genética , Animales , Cromatina/genética , Daño del ADN/genética , Heterogeneidad Genética , Inestabilidad Genómica , Humanos , Mamíferos , Subunidades de Proteína/genética , Complejo Shelterina , Proteínas de Unión a Telómeros/genéticaRESUMEN
We present biochemical evidence for an intercellular signal transduction pathway in B. subtilis. This pathway governs the conversion of the proprotein pro-sigma E to mature transcription factor sigma E. Proteolytic processing is mediated by the membrane protein SpollGA and is triggered by the inferred extracellular signal protein SpollR. A factor in conditioned medium from B. subtilis cells engineered to produce SpollR during growth triggered processing in protoplasts of B. subtilis cells that had been engineered to produce SpollGA and pro-sigma E. The factor was also detected in, and partially purified from, extracts of SpollR-producing cells of E. coli. We speculate that SpollGA is both a receptor and a protease and the SpollR interacts with SpollGA on the outside of the cytoplasmic membrane, activating the intracellular protease domain of SpollGA.