RESUMO
20-Hydroxyecdysone induces poly(A) shortening and the subsequent degradation of transcripts encoding the larval glue protein LGP-1 in Drosophila virilis late third larval instar salivary glands. Degradation concurs with the transient increase of ribonucleolytic activities in the gland cells. In vitro nuclease assays using crude cytoplasmic extracts of ecdysone-treated salivary glands demonstrate degradation to be deadenylation-independent and that the induced ribonucleolytic activities initiate the degradation of the Lgp-1 transcripts in putative single-stranded loop regions. The independence of degradation from deadenylation is also found in vivo in transformed D. melanogaster carrying a modified Lgp-1 gene.
Assuntos
Drosophila/genética , Ecdisona/farmacologia , Estabilidade de RNA/efeitos dos fármacos , Glândulas Salivares/metabolismo , Animais , Animais Geneticamente Modificados , Técnicas de Cultura , Indução Enzimática/efeitos dos fármacos , Proteínas do Grude Salivar de Drosophila/genética , Larva/genética , Metamorfose Biológica , Modelos Moleculares , Poli A/metabolismo , RNA Mensageiro/metabolismo , Ribonucleases/efeitos dos fármacos , Ribonucleases/metabolismoRESUMO
In Drosophila virilis, the three clusters of 5S rRNA genes on chromosome 5 comprise two different gene families (B and C), which differ profoundly in the organization of their spacer sequences. While C-type genes, which are found in two of the clusters, exhibit a true repetitive character, the B-type genes of the third cluster are each embedded in completely different genomic environments. Southern blots of genomic DNA of different D. virilis subspecies, D. hydei and D. melanogaster probed with 5S rRNA gene spacer and coding sequences demonstrate the specificity of C-type sequences for the D. virilis species group. The comparative analysis of flanking sequences of 5S rRNA genes of D. virilis, members of the D. melanogaster species subgroup and of the blowfly Calliphora erythrocephala reveals the existence of conserved sequence motifs both in the 5' upstream and 3' downstream flanking regions. Their possible roles in the control of expression and processing of the 5S rRNA precursor molecule are discussed.
