Ribosomal DNA (rDNA) replication origins of Saccharomyces cerevisiae are known to function inefficiently, both in the context of the tandem rDNA repeats in the chromosome and as single copy autonomously replicating sequences (ARSs) in plasmids. Here we examined components of the rDNA ARS that might contribute to inefficient extrachromosomal replication. Like the efficient H4 ARS, the rDNA ARS requires a match to the 11 bp ARS consensus sequence (ACS) and a broad non-conserved region that may contain multiple elements, including a DNA unwinding element (DUE). Using a single-strand-specific nuclease hypersensitivity assay and by determining the superhelical density required for stable DNA unwinding, we found that the DNA of the rDNA ARS is not as easily unwound as the H4 ARS. Unwinding of the rDNA ARS required additional energy, similar to the unwinding of mutations in the H4 ARS that stabilize the double helix in the DUE region and impair replication. In vivo extrachromosomal replication of the rDNA ARS was cold sensitive, like H4 ARS mutants that require additional energy to unwind the DUE region but unlike the easily unwound, wild-type H4 ARS. Impairment of replication function at reduced temperature suggests that the elevated energy requirement for DNA unwinding inherent in the wild-type rDNA ARS contributes to inefficient replication function. We also examined the essential ACS match in the rDNA ARS, which is known to be imperfect at one position. A point mutation in the essential ACS that corrects the imperfect match increased the efficiency of extrachromosomal replication. Our results reveal that the essential ACS element and DNA unwinding in the rDNA ARS are naturally impaired, suggesting that inefficient function of the rDNA replication origin has a biological purpose.
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Evidence ID | Analyze ID | Gene/Complex | Systematic Name/Complex Accession | Qualifier | Gene Ontology Term ID | Gene Ontology Term | Aspect | Annotation Extension | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Phenotype | Experiment Type | Experiment Type Category | Mutant Information | Strain Background | Chemical | Details | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Disease Ontology Term | Disease Ontology Term ID | Qualifier | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Regulator | Regulator Systematic Name | Target | Target Systematic Name | Direction | Regulation of | Happens During | Regulator Type | Direction | Regulation Of | Happens During | Method | Evidence | Strain Background | Reference |
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Site | Modification | Modifier | Source | Reference |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Allele | Assay | Annotation | Action | Phenotype | SGA score | P-value | Source | Reference | Note |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Assay | Annotation | Action | Modification | Source | Reference | Note |
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Complement ID | Locus ID | Gene | Species | Gene ID | Strain background | Direction | Details | Source | Reference |
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Evidence ID | Analyze ID | Dataset | Description | Keywords | Number of Conditions | Reference |
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