Dense cluster of genes is located at the ecdysone-regulated 3C puff of Drosophila melanogaster.
The 3C11-12 polytene bands of the Drosophila melanogaster X chromosome give rise to a prominent puff, whose regression is triggered by the increase in the titre of the steroid hormone 20-hydroxyecdysone occurring before the metamorphosis. Here, we report the molecular characterization of three genes, named ng-2, ng-3 and ng-4, which we found to be closely linked to each other and to Sgs-4, Pig-1 and ng-1, three other genes previously mapped at this polytene region. All six genes are, in fact, arranged in a tightly linked cluster spanning a DNA segment of only 11 kb. With the exception of ng-4, all the clustered genes are highly expressed only during the larval life and share the same tissue-specificity, being mainly transcribed within the salivary glands. In addition, two members of the cluster, ng-1 and ng-2, show a very high degree of sequence homology, clearly indicating that they are related to each other by means of a duplication event. Interestingly to note, the entire cluster shows a peculiar genomic location, extending across two introns of the memory gene dunce, a large gene of Drosophila whose organization has proved to be remarkably complex.
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Dipartimento di Genetica, Biologia Generale e Molecolare, Università di Napoli, Italy.
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002843:Chromatin / Q000648:ultrastructure; D002874:Chromosome Mapping; D002875:Chromosomes / Q000648:ultrastructure*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D004441:Ecdysterone / Q000494:pharmacology; D017344:Genes, Insect / Q000187:drug effects / Q000235:genetics*; D008040:Genetic Linkage; D007814:Larva; D008675:Metamorphosis, Biological / Q000187:drug effects; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D012471:Salivary Proteins and Peptides / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D002843:Chromatin; D029721:Drosophila Proteins; D012471:Salivary Proteins and Peptides; C081602:ng1 protein, Drosophila; C081603:ng2 protein, Drosophila; D004441:Ecdysterone