RESUMEN
Numerous human disorders, including Cockayne syndrome, UV-sensitive syndrome, xeroderma pigmentosum, and trichothiodystrophy, result from the mutation of genes encoding molecules important for nucleotide excision repair. Here, we describe a syndrome in which the cardinal clinical features include short stature, hearing loss, premature aging, telangiectasia, neurodegeneration, and photosensitivity, resulting from a homozygous missense (p.Ser228Ile) sequence alteration of the proliferating cell nuclear antigen (PCNA). PCNA is a highly conserved sliding clamp protein essential for DNA replication and repair. Due to this fundamental role, mutations in PCNA that profoundly impair protein function would be incompatible with life. Interestingly, while the p.Ser228Ile alteration appeared to have no effect on protein levels or DNA replication, patient cells exhibited marked abnormalities in response to UV irradiation, displaying substantial reductions in both UV survival and RNA synthesis recovery. The p.Ser228Ile change also profoundly altered PCNA's interaction with Flap endonuclease 1 and DNA Ligase 1, DNA metabolism enzymes. Together, our findings detail a mutation of PCNA in humans associated with a neurodegenerative phenotype, displaying clinical and molecular features common to other DNA repair disorders, which we showed to be attributable to a hypomorphic amino acid alteration.
Asunto(s)
Trastornos por Deficiencias en la Reparación del ADN/genética , Proteínas Mutantes/genética , Mutación Missense , Antígeno Nuclear de Célula en Proliferación/genética , Adolescente , Adulto , Envejecimiento Prematuro/genética , Sustitución de Aminoácidos , Niño , Cromosomas Humanos Par 20/genética , Análisis Mutacional de ADN , Trastornos por Deficiencias en la Reparación del ADN/patología , Trastornos por Deficiencias en la Reparación del ADN/fisiopatología , Enanismo/genética , Femenino , Pérdida Auditiva/genética , Homocigoto , Humanos , Masculino , Modelos Moleculares , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Degeneración Nerviosa/genética , Linaje , Fenotipo , Trastornos por Fotosensibilidad/genética , Antígeno Nuclear de Célula en Proliferación/química , Antígeno Nuclear de Célula en Proliferación/metabolismo , Estructura Cuaternaria de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Síndrome , Telangiectasia/genéticaRESUMEN
We report a soft tissue sarcoma from the thigh with morphologic features resembling Ewing sarcoma, clear cell sarcoma, and myoepithelial tumor of soft tissue. In addition, the genetic and immunohistochemical findings do not correspond to any established pattern, so the tumor does not clearly fit into any one classification. The karyotype analysis revealed a rare chromosomal rearrangement, t(6;22)(p22;q12), that previously has been reported in bone and epithelial tumors. Molecular studies confirmed the presence of an EWSR1-POU5F1 fusion creating a chimeric gene with the N-terminal transcriptional activation domain of EWSR1 and the C-terminal POU DNA binding domain of POU5F1. This report is novel in that to our knowledge, it is the first complete molecular characterization of an EWSR1-POU5F1 fusion in a soft tissue sarcoma. Evaluation of existing data on the known EWSR1-POU5F1 tumors suggests that the fusion gene functions in a wide variety of cell types and may modify the differentiation state of cells, resulting in susceptibility to tumorigenesis.
Asunto(s)
Proteínas de Unión a Calmodulina/genética , Diferenciación Celular , Cromosomas Humanos Par 22/genética , Cromosomas Humanos Par 6/genética , Factor 3 de Transcripción de Unión a Octámeros/genética , Proteínas de Fusión Oncogénica/genética , Proteínas de Unión al ARN/genética , Sarcoma/genética , Translocación Genética/genética , Secuencia de Aminoácidos , Secuencia de Bases , Niño , Análisis Citogenético , Femenino , Humanos , Técnicas para Inmunoenzimas , Imagen por Resonancia Magnética , Datos de Secuencia Molecular , Pronóstico , Proteína EWS de Unión a ARN , Sarcoma/diagnóstico , Sarcoma/terapiaAsunto(s)
Trasplante de Médula Ósea , Neoplasias del Sistema Nervioso Central/secundario , Leucemia Mielógena Crónica BCR-ABL Positiva/patología , Leucemia Mielógena Crónica BCR-ABL Positiva/terapia , Adulto , Crisis Blástica/complicaciones , Crisis Blástica/diagnóstico , Trasplante de Médula Ósea/fisiología , Neoplasias del Sistema Nervioso Central/complicaciones , Neoplasias del Sistema Nervioso Central/diagnóstico , Neoplasias del Sistema Nervioso Central/genética , Humanos , Hibridación Fluorescente in Situ , Leucemia Mielógena Crónica BCR-ABL Positiva/genética , Masculino , RecurrenciaRESUMEN
Cytogenetic deletions and/or loss of heterozygosity (LOH) of the short arm of chromosome 3, often with a break at 3p14, are well documented in lung tumors. The coincidence of a chromosomal fragile site, FRA3B, at a common chromosomal breakpoint in lung cancer has suggested that fragility at this site may predispose to breakage that could contribute to multistep carcinogenesis. This idea is supported by the more recent finding that FRA3B maps within the FHIT (fragile histadine triad) gene, and that aberrant transcripts and genomic deletions of FHIT/FRA3B occur in a variety of tumors including lung tumors. To determine whether some individuals have increased fragility of FRA3B that might increase the risk for breakage or deletion in 3p14.2, fragile site expression was examined in smokers, nonsmokers, and small cell lung cancer (SCLC) patients. The data clearly show that active smokers exhibit a significantly higher frequency of fragile site expression, including FRA3B, compared to that of nonsmokers and patients diagnosed with SCLC who have stopped smoking. These results suggest that active tobacco exposure increases chromosome fragile site expression, and that this fragility is transient and reversible. The data support the hypothesis that exposure to tobacco carcinogens increases the potential for chromosome breakage at fragile sites.