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Updated: Aug 9, 2026

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique
Published on: October 27, 2011
Distal sequences, but not ori-beta/OBR-1, are essential for initiation of DNA replication in the Chinese hamster DHFR
R F Kalejta1, X Li, L D Mesner
1Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville 22908, USA.
Abstract:
In the Chinese hamster dihydrofolate reductase replication initiation zone, the ori-beta locus is preferred over other start sites. To test the hypothesis that ori-beta contains a genetic replicator, we restored a deletion in the 3' end of the DHFR gene with a cosmid that provides the missing sequence and simultaneously knocks out the downstream ori-beta locus. Replication initiates normally in ori-beta knockout cell lines, and the DHFR domain is still synthesized in early S phase. However, initiation is completely suppressed in the starting deletion variant lacking the 3' end of the gene. We conclude that ori-beta does not contain an essential replicator, but that distant sequence elements have profound effects on origin activity in this locus.
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