RESUMEN
Hypoxia, an insufficient level of oxygen in the cell, occurs during normal activity and also in pathological conditions such as ischemia and tumorigenesis. Although many hypoxia-response genes have been identified, an understanding of the functional role for these genes in the living animal is lacking. Here we present a genome-wide study of gene expression changes during hypoxia and then functionally test a subset of these genes for roles in survival and recovery from hypoxia. We found 79 genes with increased mRNA levels when adult flies were treated with 0.5% O2 for 6 h. A subset of these genes had detectably increased levels in as short as 1 h of low-oxygen treatment. Mild hypoxia levels resulted in an increase in transcription levels for only 20 genes. Viability during hypoxia and recovery time from hypoxia-induced paralysis was examined in flies with a reduction in activity in hypoxia-response genes. The observed decreased viability and increased recovery time from paralysis in many of the lines demonstrate that the increased transcript levels seen after hypoxia are important for the response to low oxygen.
Asunto(s)
Hipoxia de la Célula/genética , Drosophila melanogaster/genética , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Carboxiliasas/genética , Carboxiliasas/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Enzimas Multifuncionales , Mutación , Análisis de Secuencia por Matrices de Oligonucleótidos , Parálisis/genética , Parálisis/metabolismo , Péptido Sintasas/genética , Péptido Sintasas/metabolismo , ARN Mensajero/metabolismo , Proteínas Represoras , Reproducibilidad de los Resultados , Factores de TiempoRESUMEN
The beta-globin locus control region (LCR) is a powerful regulatory element required for high-level globin gene expression. We have generated transgenic mouse lines carrying a beta-globin locus yeast artificial chromosome lacking the LCR to determine if the LCR is required for globin gene activation. beta-Globin gene expression was analyzed by RNase protection, but no detectable levels of epsilon-, gamma- and beta-globin gene transcripts were produced at any stage of development. These findings suggest that the presence of the LCR is a minimum requirement for globin gene expression. Next, we tested whether the LCR is necessary to activate globin gene expression in a gamma-globin promoter mutant that causes hereditary persistence of fetal hemoglobin (HPFH). beta-YAC transgenic mice carrying the -117 HPFH mutation and a HS3 core deletion that specifically abolishes gamma-globin gene expression during definitive erythropoiesis were produced to test whether the -117 (A)gamma promoter is activated in the absence of interaction with the LCR. In four transgenic mouse lines, gamma-globin gene expression was absent in adult erythrocytes, suggesting that an interaction between the gamma-globin gene promoter and the LCR is required for gamma gene activation even when the promoter contains an HPFH mutation.