Journal
GENES & DEVELOPMENT
Volume 19, Issue 23, Pages 2827-2836Publisher
COLD SPRING HARBOR LAB PRESS, PUBLICATIONS DEPT
DOI: 10.1101/gad.1369805
Keywords
replication; episome; GAL4; ORC; origin; licensing; Cdc6
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Funding
- NCI NIH HHS [CA60499, R01 CA089406-05, CA89406, R01 CA060499, R01 CA060499-12, R01 CA089406] Funding Source: Medline
- NIGMS NIH HHS [GM053504, R01 GM053504] Funding Source: Medline
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Origins of replication are expected to recruit initiation proteins like origin recognition complex (ORC) and Cdc6 in eukaryotes and provide a platform for unwinding DNA. Here we test whether localization of initiation proteins onto DNA is sufficient for origin function. Different components of the ORC complex and Cdc6 stimulated prereplicative complex (pre-RC) formation and replication initiation when fused to the GAL4 DNA-binding domain and recruited to plasmid DNA containing a tandem array of GAL4-binding sites. Replication occurred once per cell cycle and was inhibited by Geminin, indicating that the plasmid was properly licensed during the cell cycle. The GAL4 fusion protein recruits other polypeptides of the ORC-Cdc6 complex, and nascent strand abundance was highest near the GAL4-binding sites. Therefore, the artificial origin recapitulates many of the regulatory features of physiological origins and is valuable for studies on replication initiation in mammalian cells. We demonstrated the utility of this system by showing the functional importance of the ATPase domains of human Cdc6 and Orc1 and the dispensability of the N-terminal segments of Orc1 and Orc2 in this assay. Artificial recruitment of a eukaryotic cellular replication initiation factor to a DNA sequence can create a functional origin of replication, providing a robust genetic assay for these factors and a novel approach to generating episomal vectors for gene therapy.
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