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Gene Review

Cp18  -  Chorion protein 18

Drosophila melanogaster

Synonyms: ACE3, CG6517, CP18, Chorion protein S18, Dmel\CG6517, ...
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High impact information on Cp18

  • Two elements important for amplification of the third chromosome chorion gene cluster, ACE3 and Ori-beta, are directly bound by Orc (origin recognition complex), and two-dimensional gel analysis has revealed that the primary origin used is Ori-beta (refs 7-9) [1].
  • To demonstrate that the in vivo localization of DmORC is related to its DNA-binding properties, we find that purified DmORC binds to ACE3 and AER-d in vitro, and like its S. cerevisiae counterpart, this binding is dependent on ATP [2].
  • Drosophila ORC specifically binds to ACE3, an origin of DNA replication control element [2].
  • However, initiation was nonrandom; the majority of initiations appeared to occur near the Bgl II site located between the s18 and s15 chorion genes [3].
  • The role of ACE3 in Drosophila chorion gene amplification [4].

Biological context of Cp18

  • One long intergenic sequence, located in the distal 5' flanking region of gene s18, is homologous to ACE3, a major amplification control element and contains an 80-bp A/T-rich sequence, known to stimulate strong binding of the origin recognition complex (ORC) in D. melanogaster [5].
  • Therefore ACE3 does not appear to be analogous to a transcription enhancer [4].
  • We have characterized at the nucleotide level a 4.8-kilobase pair segment of the third chromosome of Drosophila melanogaster, which contains a cluster of three chorion genes, s18-1, s15-1 and s19-1 [6].
  • The highest number of dyad symmetries, reminiscent of sequences that function as viral replication origins, is found associated with the T- and A-rich regions between genes s18-1 and s15-1 [6].
  • Here we present the complete nucleotide sequence of this "amplification control element" and of genes encoding the chorion structural proteins s18-1 and s15-1, which are contained within it [7].

Anatomical context of Cp18

  • The parent construct supported 18- to 20-fold amplification, and contained the 320 bp ACE3, the approximately 1.2 kb S18 chorion gene and the 840 bp ori-beta [8].
  • We have used two types of deletions in the chorion cluster: the first was in vitro generated deletions of the ACE-3 region that were subsequently introduced into the germ line, and the second was deletions induced in vivo within a transposon at a preexisting chromosomal location, thus avoiding the complication of position effects [9].
  • Constructs containing chimeric combinations of Drosophila melanogaster and D. grimshawi DNA regions, as well as D. grimshawi sequences alone, can direct expression in the follicular epithelium, in an s18-specific temporal and spatial pattern [10].

Other interactions of Cp18

  • Despite marked temporal differences in their accumulation profiles, s36 and s18, putative chorion proteins, were similarly distributed throughout the floor, pillars, and roof of the endochorion [11].
  • Using immunolocalization, we observe that ACE3, a 440-bp chorion element that contains information sufficient to drive amplification, directs DmORC localization in follicle cells [2].


  1. Role for a Drosophila Myb-containing protein complex in site-specific DNA replication. Beall, E.L., Manak, J.R., Zhou, S., Bell, M., Lipsick, J.S., Botchan, M.R. Nature (2002) [Pubmed]
  2. Drosophila ORC specifically binds to ACE3, an origin of DNA replication control element. Austin, R.J., Orr-Weaver, T.L., Bell, S.P. Genes Dev. (1999) [Pubmed]
  3. Multiple replication origins are used during Drosophila chorion gene amplification. Heck, M.M., Spradling, A.C. J. Cell Biol. (1990) [Pubmed]
  4. The role of ACE3 in Drosophila chorion gene amplification. Orr-Weaver, T.L., Johnston, C.G., Spradling, A.C. EMBO J. (1989) [Pubmed]
  5. The chorion genes of the medfly. II. DNA sequence evolution of the autosomal chorion genes s18, s15, s19 and s16 in Diptera. Vlachou, D., Komitopoulou, K. Gene (2001) [Pubmed]
  6. Coding and potential regulatory sequences of a cluster of chorion genes in Drosophila melanogaster. Wong, Y.C., Pustell, J., Spoerel, N., Kafatos, F.C. Chromosoma (1985) [Pubmed]
  7. DNA sequence of a 3.8 kilobase pair region controlling Drosophila chorion gene amplification. Levine, J., Spradling, A. Chromosoma (1985) [Pubmed]
  8. Sequence requirements for function of the Drosophila chorion gene locus ACE3 replicator and ori-beta origin elements. Zhang, H., Tower, J. Development (2004) [Pubmed]
  9. Amplification-control element ACE-3 is important but not essential for autosomal chorion gene amplification. Swimmer, C., Delidakis, C., Kafatos, F.C. Proc. Natl. Acad. Sci. U.S.A. (1989) [Pubmed]
  10. Positive and negative DNA elements of the Drosophila grimshawi s18 chorion gene assayed in Drosophila melanogaster. Swimmer, C., Kashevsky, H., Mao, G., Kafatos, F.C. Dev. Biol. (1992) [Pubmed]
  11. Eggshell assembly in Drosophila: processing and localization of vitelline membrane and chorion proteins. Pascucci, T., Perrino, J., Mahowald, A.P., Waring, G.L. Dev. Biol. (1996) [Pubmed]
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