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Rereplication phenomenon in fission yeast requires MCM proteins and other S phase genes
1The Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA.
Abstract:
The fission yeast Schizosaccharomyces pombe can be induced to perform multiple rounds of DNA replication without intervening mitoses by manipulating the activity of the cyclin-dependent kinase p34(cdc2). We have examined the role in this abnormal rereplication of a large panel of genes known to be involved in normal S phase. The genes analyzed can be grouped into four classes: (1) those that have no effect on rereplication, (2) others that delay DNA accumulation, (3) several that allow a gradual increase in DNA content but not in genome equivalents, and finally, (4) mutations that completely block rereplication. The rereplication induced by overexpression of the CDK inhibitor Rum1p or depletion of the Cdc13p cyclin is essentially the same and requires the activity of two minor B-type cyclins, cig1(+) and cig2(+). In particular, the level, composition, and localization of the MCM protein complex does not alter during rereplication. Thus rereplication in fission yeast mimics the DNA synthesis of normal S phase, and the inability to rereplicate provides an excellent assay for novel S-phase mutants.
Insights
Fission yeast can undergo DNA replication without cell division by altering cyclin-dependent kinase p34(cdc2) activity. This study identifies genes essential for normal S phase, categorizing their roles in abnormal DNA rereplication.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- The fission yeast Schizosaccharomyces pombe offers a model for studying DNA replication and cell cycle control.
- Understanding the regulation of DNA replication is crucial for comprehending cell proliferation and preventing genomic instability.
Purpose of the Study:
- To investigate the genes involved in normal S phase and their roles in abnormal DNA rereplication in Schizosaccharomyces pombe.
- To identify novel genes that regulate DNA replication through an assay for blocked rereplication.
Main Methods:
- Inducing multiple rounds of DNA replication by manipulating p34(cdc2) activity in fission yeast.
- Analyzing a panel of S-phase genes for their effects on DNA rereplication.
- Categorizing gene mutations based on their impact on DNA accumulation and genome equivalents.
Main Results:
- Genes involved in normal S phase were classified into four groups based on their effect on DNA rereplication: no effect, delayed accumulation, gradual increase without genome doubling, or complete block.
- Rereplication induced by Rum1p overexpression or Cdc13p depletion requires the activity of cig1(+) and cig2(+) cyclins.
- The MCM protein complex composition and localization remain unchanged during rereplication.
Conclusions:
- DNA rereplication in fission yeast effectively mimics normal S-phase DNA synthesis.
- The observed inability to rereplicate serves as a valuable screening method for identifying new S-phase regulatory genes.