Drosophila chorion gene amplification requires an upstream region regulating s18 transcription.
A cluster of Drosophila melanogaster chorion genes at locus 66D on the third chromosome amplifies 60-fold in the ovarian follicle cells prior to the onset of gene expression. A 3.8-kilobase (kb) region of the gene cluster can induce tissue-specific amplification in transformants. Previous models postulated that amplification is activated in follicle cells by transcription of one of the two chorion genes (s15 and s18) located within the 3.8-kb essential region. In this study, we showed that neither s15 nor s18 chorion gene transcription was required for amplification. However, a 510-bp region upstream from s18 contained sequences essential for both amplification and s18 transcription. No other region within the 3.8-kb fragment was required for amplification. We propose that upstream transcription control elements rather than transcription per se are involved in controlling amplification during development.
D000818:Animals; D001483:Base Sequence; D002823:Chorion / Q000502:physiology; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D004331:Drosophila melanogaster / Q000235:genetics*; D005260:Female; D005784:Gene Amplification; D005809:Genes, Regulator; D010957:Plasmids; D014158:Transcription, Genetic