RESUMEN
The cDNA sequence of foot-specific peroxidase PPOD1 from the Chinese strain of Hydra magnipapillata was cloned by reverse transcription-polymerase chain reaction. The cDNA sequence contained a coding region with an 873-bp open reading frame, a 31-bp 5'-untranslated region, and a 36-bp 3'-untranslated region. The structure prediction results showed that PPOD1 contains 10.34% of α-helix, 38.62% of extended strand, 12.41% of ß-turn, and 38.62% of random coil. The structural core was α-helix at the N terminus. The GenBank protein blast server showed that PPOD1 contains 2 fascin-like domains. In addition, high-level PPOD1 activity was only present in the ectodermal epithelial cells located on the edge of the adhesive face of the basal disc, and that these cells extended lamellipodia and filopodia when the basal disc was tightly attached to a glass slide. The fascin-like domains of Hydra PPOD1 might contribute to the bundling of the actin filament of these cells, and hence, the formation of filopodia. In conclusion, these cells might play an important role in strengthening the adsorbability of the basal disc to substrates.
Asunto(s)
Regulación Enzimológica de la Expresión Génica , Hydra/genética , Sistemas de Lectura Abierta/genética , Peroxidasa/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Sitios de Unión/genética , China , Clonación Molecular , ADN Complementario/química , ADN Complementario/genética , Hydra/enzimología , Modelos Moleculares , Datos de Secuencia Molecular , Peroxidasa/clasificación , Peroxidasa/metabolismo , Filogenia , Células Procariotas/metabolismo , Estructura Terciaria de Proteína , Seudópodos/enzimología , Seudópodos/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Análisis de Secuencia de ADN , Homología de Secuencia de AminoácidoRESUMEN
O6-methylguanine-DNA methyltransferase (MGMT) is a major determinant of susceptibility to methylating carcinogens and of tumor resistance to anticancer methylating and chloroethylating drugs. The silencing of MGMT expression that occurs in 20-30% of human tumor lines is tightly linked to methylation within the MGMTgene 5'CpG island. Previous studies on a very limited number of cell lines showed that such methylation was uneven, with hot-spots where methylation almost invariably occurred and intervening regions with very low incidences of methylation. To ascertain if such hot-spot methylation is in fact a ubiquitous hallmark of MGMT-silenced cells, we determined the methylation status of selected hot-spot CpGs in an extensive panel of MGMT-expressing and -silenced cell lines and xenografts. Using two simple and rapid bisulfite-polymerase chain reaction-based assays, we confirmed that in MGMT-silenced cells, methylation occurred at these sites whereas it was essentially absent in MGMT-expressing cells.
Asunto(s)
Islas de CpG/genética , Genoma Humano , O(6)-Metilguanina-ADN Metiltransferasa/genética , Línea Celular , Mapeo Cromosómico , Metilación de ADN , Humanos , Regiones Promotoras Genéticas/genéticaRESUMEN
The mechanism whereby the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) is silenced in repair-deficient (Mer-) human tumor cells is unknown. The role of methylation of the 5' CpG island in MGMT gene suppression is controversial. Although we previously showed by restriction enzyme analysis that CpG methylation in this region was associated with gene suppression, methylation at such sites was generally incomplete, suggesting heterogeneity. To clarify this issue, we have unequivocally defined the methylation status of every CpG by genomic sequencing of individual cloned copies of bisulfite-modified DNA. The region from -249 to +259 at the transcription start site was virtually methylation free in HT29 cells (Mer+), whereas in BE or HeLa S3 cells (Mer-), this region was substantially methylated in every DNA copy, with "hot spots" from -249 to -103 and from +107 to +196. Up-regulation of MGMT in HeLa S3 cells induced by 5-azacytidine was accompanied by progressive demethylation and the appearance of totally unmethylated copies of DNA. We conclude that, in Mer- cells, the MGMT promoter contains specific CpG methylation hot spots that are tightly linked to and are potential markers of gene silencing.
Asunto(s)
Islas de CpG/genética , Metilación de ADN , Metiltransferasas/genética , Represión Enzimática/genética , Regulación Enzimológica de la Expresión Génica/genética , Regulación Neoplásica de la Expresión Génica/genética , Células HT29 , Células HeLa , Humanos , Metiltransferasas/metabolismo , O(6)-Metilguanina-ADN Metiltransferasa , Análisis de Secuencia de ADN , Transcripción Genética , Células Tumorales CultivadasRESUMEN
Sixty-five patients in Xinjiang with syndrome of endemic arsenism and fluorosis (SEAF) were investigated clinically from March 1982 to August 1989. SEAF is a kind of chronic syndrome resulting from the combined, harmful effects of two trace elements, arsenic and fluorine. Peripheral neuritis and cardiovascular changes were observed in this syndrome more often than in simple arsenism or simple fluorosis. The excessive quantities of these two trace elements in blood might have a synergic, harmful effect on the nervous and circulatory systems. No definite conclusion could be reached with regard to the morbidity of skin and visceral tumors in this series. The incidence of associated skin cancer was found to be 7.7% and an associated Grade II squamous cell carcinoma of the esophagus was encountered in one patient.
Asunto(s)
Intoxicación por Arsénico , Intoxicación por Flúor/diagnóstico , Contaminantes Químicos del Agua/efectos adversos , Adolescente , Adulto , Anciano , Niño , Mareo/diagnóstico , Femenino , Intoxicación por Flúor/etiología , Humanos , Masculino , Persona de Mediana Edad , Síndrome , Abastecimiento de Agua/análisisRESUMEN
A patient with pemphigus foliaceus, derived from pemphigus erythematosus, developed Kaposi's sarcoma characterized by wide-spread skin nodules on the extremities after 5-month treatment with large doses of prednisone. The patient died one year later. We conclude that the immunosuppressive treatment with prolonged large doses of prednisone is attributable to the impairment of cellular immunity and the evolution of Kaposi's sarcoma.