Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Comparative genomic hybridization of S. pombe co-overexpressing DNA synthesis initiation factors cdc18 (cdc6) and cdt1 to investigate gene copy number increases

ABSTRACT: During S-phase of the eukaryotic cell cycle, controls exist to ensure that replication origins fire only once and become inactivated after traverse of a replication fork. Failure of these controls results in local amplification of the genome which can lead to gene copy increases important for both evolutionary change and for somatic genetic diseases such as cancer. It is not known what characteristics of replication origins might predispose them to escape from these controls. We have investigated this problem in the fission yeast Schizosaccharomyces pombe by characterizing regions of the genome which become amplified when the DNA synthesis initiation factors cdc18 (cdc6) and cdt1 are co-overexpressed and by defining origins of replication responsible for local amplification. We find that a single origin can be necessary but not sufficient to induce ectopic local amplification and that origins likely to escape the regulation of one firing per cell cycle are among the most AT-rich, efficient and early firing in the genome, and are embedded in long intergenes. Replication origins with these features may be more prone to re-fire within a round of replication potentiating genome instability.

ORGANISM(S): Schizosaccharomyces pombe

SUBMITTER: Christian Heichinger

PROVIDER: E-MTAB-139 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Specific replication origins promote DNA amplification in fission yeast.

Kiang Lee L Heichinger Christian C Watt Stephen S Bähler Jürg J Nurse Paul P

Journal of cell science 20100824 Pt 18

To ensure equal replication of the genome in every eukaryotic cell cycle, replication origins fire only once each S phase and do not fire after passive replication. Failure in these controls can lead to local amplification, contributing to genome instability and the development of cancer. To identify features of replication origins important for such amplification, we have investigated origin firing and local genome amplification in the presence of excess helicase loaders Cdc18 and Cdt1 in fissi ...[more]

PMID: 20736315

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Project description:To achieve faithful replication of the genome once in each cell cycle, re-initiation of S-phase is prevented in G2 and origins are restricted from re-firing within S-phase. We have investigated the block to re-replication during G2 in fission yeast. The DNA synthesis that occurs when G2/M cyclin dependent kinase (CDK) activity is depleted has been assumed to be repeated rounds of S-phase without mitosis but this has not been demonstrated to be the case. In a normal mitotic S-phase, the genome is uniformly replicated with no areas amplified relative to other regions, so there is an equal copy number of each portion of the genome. To determine whether equal rounds of replication or local amplification occurred in the cdc13 s/o strain we assayed genomic DNA from cells which had increased their DNA content to 16C-32C. Using microarrays, we measured the relative DNA content across the genome, using DNA from control G1-arrested cells as a reference. This experiment revealed that replication was essentially equal across the genome, with no region becoming significantly amplified to a higher copy number than any other. Since the genome was found to be essentially evenly replicated as would be expected if each round of replication corresponded to a normal S-phase, we investigated whether this was the result of a normal replication program at the level of origin firing. We asked whether S-phase origins are used to reduplicate the genome, and whether origins are used with the same efficiency as in wild type cells. We identified the origins utilized in the first endoreduplication cycle of cdc13 s/o using microarray analyses of cells treated with 11 mM HU. Samples were taken at 5 hours when most cells of the culture not treated with HU had undergone a doubling in DNA content. A total of 799 origins were identified, a number roughly similar to the 904 identified in a normal S-phase. We show here that on G2/M CDK depletion in G2, repeated S-phases are induced. Mostly normal mitotic S-phase origins were utilized although at different efficiencies, and replication was essentially equal across the genome. We conclude that CDK inhibits re-initiation of S-phase during G2, and if G2/M CDK is depleted replication results from induction of a largely normal S-phase program with only small differences in origin usage and efficiency.

Dataset Information

Comparative genomic hybridization of S. pombe co-overexpressing DNA synthesis initiation factors cdc18 (cdc6) and cdt1 to investigate gene copy number increases

Publications

Specific replication origins promote DNA amplification in fission yeast.

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