title: Functionally distinct, sequence-specific replicator and origin elements are required for Drosophila chorion gene amplification.
abstract: To meet the demand for the rapid synthesis of chorion (eggshell) proteins, Drosophila ovarian follicle cells amplify the chromosomal loci containing the chorion gene clusters up to 60-fold. Amplification occurs by repeated firing of one or more origins located within each gene cluster. Deletion analyses of transgenic constructs derived from the third chromosome cluster have identified a 320-bp amplification control element (ACE3) required for amplification, as well as several stimulatory amplification enhancing regions (AERs). Two-dimensional (2D) gel analyses have identified multiple DNA replication initiation sites (origins) that partially overlap in location with ACE3 and the AERs. To further study sequence requirements for amplification, a vector was used in which transgenic constructs are protected from chromosomal position effects by flanking insulator elements, the suppressor Hairy-wing protein binding site (SHWBS). Using the buffered vector, the 320-bp ACE3 and an 884-bp element designated ori-beta were found to be necessary and sufficient for amplification. Two-dimensional gels revealed that ori-beta was acting as the origin. In contrast, origin activity could not be detected for ACE3. An insulator placed between ACE3 and ori-beta inhibited amplification, indicating that ACE3 activates ori-beta in cis. The results suggest that ACE3 acts as a replicator and support and extend the replicator model for the organization of metazoan chromosomal replicons.
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-1340, USA.
authors.forename: L
authors.initials: L
authors.lastname: Lu
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Tower
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002823:Chorion / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins; D004527:Egg Proteins / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D005784:Gene Amplification; D017344:Genes, Insect; D019476:Insect Proteins / Q000096:biosynthesis / Q000235:genetics*; D005810:Multigene Family; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D018741:Replication Origin; D012097:Repressor Proteins
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D004527:Egg Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; C015753:chorion proteins; C083738:su(Hw) protein, Drosophila