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Mol Cell Biol. 2001 Feb;21(4):1098-110.

The Chinese hamster dihydrofolate reductase replication origin beta is active at multiple ectopic chromosomal locations and requires specific DNA sequence elements for activity.

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Department of Molecular Biology and Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37232-6838, USA.

Erratum in

  • Mol Cell Biol 2002 Sep;22(17):6319.


To identify cis-acting genetic elements essential for mammalian chromosomal DNA replication, a 5.8-kb fragment from the Chinese hamster dihydrofolate reductase (DHFR) locus containing the origin beta (ori-beta) initiation region was stably transfected into random ectopic chromosomal locations in a hamster cell line lacking the endogenous DHFR locus. Initiation at ectopic ori-beta in uncloned pools of transfected cells was measured using a competitive PCR-based nascent strand abundance assay and shown to mimic that at the endogenous ori-beta region in Chinese hamster ovary K1 cells. Initiation activity of three ectopic ori-beta deletion mutants was reduced, while the activity of another deletion mutant was enhanced. The results suggest that a 5.8-kb fragment of the DHFR ori-beta region is sufficient to direct initiation and that specific DNA sequences in the ori-beta region are required for efficient initiation activity.

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