Regulation of origin activation during Drosophila follicle cell gene amplification

Abstract

We are utilizing the Drosophila follicle cell gene amplification system to better understand the mechanisms of DNA replication origin activation in metazoans. During gene amplification, specific origins of replication undergo repeated rounds of activation at six distinct sites in the follicle cell genome. These Drosophila Amplicons in Follicle Cells (DAFCs) utilize the same replication machinery as normal DNA replication, including the Origin Recognition Complex (ORC), DUP/Cdt1, and the MCM2–7 helicase. However, the mechanisms controlling the activation of amplification origins remain poorly understood. We identified an origin at DAFC‐62D whose activation is dependent upon transcription. We will present experiments utilizing transgenic DAFC‐62D transposon insertions to test whether transcription is required locally for origin activation. Additionally, we are investigating the effects of local chromatin on origin activation. We have identified cis‐acting position effects acting over at least 5 kb that repress ORC binding and amplification at DAFC‐22B.