RESUMEN
Trans effects at the sn-glycerol-3-phosphate dehydrogenase locus (Gpdh) of Drosophila melanogaster give rise to an increase in GPDH activity and mRNA from the wild-type allele in heterozygotes with some low-activity alleles. Either the low-activity alleles that induce the effect have a defective P-element inserted between the promoter and a downstream intronic enhancer element or the promoter region is deleted. The trans effect is pairing dependent, characteristic of transvection at some other loci. The defective P-elements that mediate transvection are located between the promoter and at least up to 6 bp downstream of the transcription start site. Transvection at Gpdh appears similar to the "enhancer action in trans" mode at the yellow locus.
Asunto(s)
Elementos Transponibles de ADN , Drosophila melanogaster/genética , Glicerolfosfato Deshidrogenasa/genética , Proteínas de Insectos/genética , Regiones Promotoras Genéticas , Animales , Secuencia de Bases , Northern Blotting , Proteínas de Unión al ADN/genética , Proteínas de Drosophila , Femenino , Glicerolfosfato Deshidrogenasa/metabolismo , Heterocigoto , Proteínas de Insectos/metabolismo , Masculino , Datos de Secuencia Molecular , ARN Mensajero , Transcripción GenéticaRESUMEN
A fourth recently discovered isozyme of sn-glycerol-3-phosphate dehydrogenase (GPDH-4) in Drosophila melanogaster is shown to be a translational product of the Gpdh transcript which contains exons 1 through 7. This transcript was also found in two other Drosophila species, D. busckii and D. virilis. In contrast to D. melanogaster and D. busckii, the Gpdh transcript containing exons 1-6 is absent in D. virilis adults. The reason for this difference between D. virilis and the two other species is intriguing but remains elusive. We have ruled out the possibility that a replacement of an amino acid residue in exon 7 played any role in generating this interspecific variation.
Asunto(s)
Drosophila/enzimología , Drosophila/genética , Glicerolfosfato Deshidrogenasa/genética , Animales , Elementos Transponibles de ADN , Drosophila/crecimiento & desarrollo , Drosophila melanogaster/enzimología , Drosophila melanogaster/genética , Exones , Regulación del Desarrollo de la Expresión Génica , Glicerol-3-Fosfato Deshidrogenasa (NAD+) , Glicerolfosfato Deshidrogenasa/metabolismo , Isoenzimas , Larva/enzimología , Transformación GenéticaRESUMEN
P element-mediated transformation has been used to investigate the regulation of expression of the sn-glycerol-3-phosphate dehydrogenase gene of Drosophila melanogaster. A 13-kb construct containing the eight exons and associated introns, 5 kb of the 5' region, and 3 kb downstream from the structural gene produced normal levels of enzyme activity and rescued the poor viability of flies lacking the enzyme. All the regulatory elements essential for normal enzyme expression were located in a fragment that included the exons and introns and 1-kb upstream noncoding sequence. Deletions of the 1.6-kb second intron reduced activity to 25%. Transformants with fusion constructs between the sn-glycerol-3-phosphate dehydrogenase gene and the beta-galactosidase gene from E. coli revealed three elements that affected expression. A (CT)9 repeat element at the 5' end of the second intron increased expression in both larvae and adults, particularly at emergence. A second regulatory element, which includes a (CT)7 repeat, was located 5' to the TATA box and had similar effects on the gene's expression. A third, undefined, enhancer was located in the second intron, between 0.5 and 1.8 kb downstream of the translation initiation codon. This element increases enzyme activity to a similar extent in larvae and adults but has little effect when the enhancer at the 5' end of the intron is present.
Asunto(s)
Drosophila melanogaster/genética , Regulación de la Expresión Génica , Glicerolfosfato Deshidrogenasa/genética , Glicerolfosfato Deshidrogenasa/fisiología , Factores de Edad , Animales , Fusión Artificial Génica , Electroforesis en Acetato de Celulosa , Modelos Biológicos , Eliminación de Secuencia , Transformación Genética , beta-Galactosidasa/metabolismoRESUMEN
We have determined the sequence of 4 Aspergillus nidulans 5S rRNA genes and compared it with 4 previously established sequences. No extensive homologies are found in 5' flanking sequences, but in the 3' flanks of two genes and two pseudogenes similar sequences are observed. In the coding sequences differences occur in 7 positions. Two 5S rRNA genes which are found in one plasmid 1.1 kb apart are located in opposite orientations.
Asunto(s)
Aspergillus nidulans/genética , Genes Fúngicos , ARN Ribosómico 5S/genética , ARN Ribosómico/genética , Secuencia de Bases , Datos de Secuencia Molecular , SeudogenesRESUMEN
The sequence of four Aspergillus nidulans 5S rRNA genes and of two pseudogenes has been determined. A conserved sequence about 100 bp upstream of the 5S rRNA coding sequences has been found in three genes and one pseudogene. The two pseudogenes correspond to the 5' half of the 5S rRNA coding sequence and their 3' flanking sequences which are not homologous to 5S rRNA are strongly conserved.