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Functionally distinct, sequence-specific replicator and origin elements are required for Drosophila chorion gene
1Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-1340, USA.
Genes & Development
|February 7, 2001
Summary
Drosophila follicle cells amplify chorion genes using an amplification control element (ACE3) that activates a DNA replication origin (ori-beta) in cis, supporting the replicator model for gene amplification.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- Drosophila ovarian follicle cells amplify chorion gene clusters up to 60-fold to meet protein synthesis demands.
- Amplification relies on repeated firing of DNA replication origins within gene clusters.
Purpose of the Study:
- To investigate the sequence requirements for chorion gene amplification.
- To identify the functional roles of the amplification control element (ACE3) and ori-beta in DNA replication initiation.
Main Methods:
- Deletion analyses of transgenic constructs.
- Two-dimensional (2D) gel electrophoresis to identify DNA replication origins.
- Use of a buffered vector with insulator elements (SHWBS) to mitigate chromosomal position effects.
Main Results:
- The 320-bp ACE3 and 884-bp ori-beta elements were found to be necessary and sufficient for amplification.
- ori-beta functioned as the DNA replication origin, while ACE3 did not show origin activity.
- An insulator between ACE3 and ori-beta inhibited amplification, indicating ACE3 activates ori-beta in cis.
Conclusions:
- ACE3 acts as a replicator, activating ori-beta to initiate DNA replication.
- These findings support and extend the replicator model for metazoan chromosomal replicons.