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Essential role of MCM proteins in premeiotic DNA replication
Karola Lindner1, Juraj Gregán, Stuart Montgomery
1Department of Zoology, University of Oxford, Oxford, OX1 3PS United Kingdom.
Abstract:
A critical event in eukaryotic DNA replication involves association of minichromosome maintenance (MCM2-7) proteins with origins, to form prereplicative complexes (pre-RCs) that are competent for initiation. The ability of mutants defective in MCM2-7 function to complete meiosis had suggested that pre-RC components could be irrelevant to premeiotic S phase. We show here that MCM2-7 proteins bind to chromatin in fission yeast cells preparing for meiosis and during premeiotic S phase in a manner suggesting they in fact are required for DNA replication in the meiotic cycle. This is confirmed by analysis of a degron mcm4 mutant, which cannot carry out premeiotic DNA replication. Later in meiosis, Mcm4 chromatin association is blocked between meiotic nuclear divisions, presumably accounting for the absence of a second round of DNA replication. Together, these results emphasize similarity between replication mechanisms in mitotic and meiotic cell cycles.
Insights
Minichromosome maintenance (MCM2-7) proteins are essential for DNA replication during the meiotic S phase in fission yeast. Their chromatin association is regulated to ensure a single round of replication during meiosis.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- Eukaryotic DNA Replication
Background:
- Prereplicative complexes (pre-RCs), formed by minichromosome maintenance (MCM2-7) proteins, are crucial for eukaryotic DNA replication initiation.
- Previous studies suggested MCM proteins might not be essential for premeiotic S phase due to mutant meiosis completion.
Purpose of the Study:
- To investigate the role of MCM2-7 proteins in DNA replication during the meiotic cell cycle in fission yeast.
- To determine if MCM proteins are required for premeiotic DNA replication and how their association is regulated during meiosis.
Main Methods:
- Chromatin association analysis of MCM2-7 proteins in meiotic fission yeast.
- Analysis of a degron mcm4 mutant to assess premeiotic DNA replication.
- Monitoring Mcm4 chromatin association during meiotic nuclear divisions.
Main Results:
- MCM2-7 proteins bind to chromatin during meiotic preparation and premeiotic S phase, indicating their requirement for meiotic DNA replication.
- A degron mcm4 mutant demonstrated an inability to perform premeiotic DNA replication.
- Mcm4 chromatin association was inhibited between meiotic nuclear divisions, preventing a second DNA replication round.
Conclusions:
- MCM proteins are essential for DNA replication in the meiotic cycle of fission yeast, similar to the mitotic cycle.
- Regulation of MCM chromatin association ensures a single round of DNA replication during meiosis.