Related Experiment Video
Updated: May 15, 2026
Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG
Published on: July 26, 2024
The fission yeast minichromosome maintenance (MCM)-binding protein (MCM-BP), Mcb1, regulates MCM function during
Venny Santosa1, Sabrina Martha, Noriaki Hirose
1Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
Abstract:
The minichromosome maintenance (MCM) complex is a replicative helicase, which is essential for chromosome DNA replication. In recent years, the identification of a novel MCM-binding protein (MCM-BP) in most eukaryotes has led to numerous studies investigating its function and its relationship to the MCM complex. However, the mechanisms by which MCM-BP functions and associates with MCM complexes are not well understood; in addition, the functional role of MCM-BP remains controversial and may vary between model organisms. The present study aims to elucidate the nature and biological function of the MCM-BP ortholog, Mcb1, in fission yeast. The Mcb1 protein continuously interacts with MCM proteins during the cell cycle in vivo and can interact with any individual MCM subunit in vitro. To understand the detailed characteristics of mcb1(+), two temperature-sensitive mcb1 gene mutants (mcb1(ts)) were isolated. Extensive genetic analysis showed that the mcb1(ts) mutants were suppressed by a mcm5(+) multicopy plasmid and displayed synthetic defects with many S-phase-related gene mutants. Moreover, cyclin-dependent kinase modulation by Cig2 repression or Rum1 overproduction suppressed the mcb1(ts) mutants, suggesting the involvement of Mcb1 in pre-RC formation during DNA replication. These data are consistent with the observation that Mcm7 loading onto replication origins is reduced and S-phase progression is delayed in mcb1(ts) mutants. Furthermore, the mcb1(ts) mutation led to the redistribution of MCM subunits to the cytoplasm, and this redistribution was dependent on an active nuclear export system. These results strongly suggest that Mcb1 promotes efficient pre-RC formation during DNA replication by regulating the MCM complex.
Insights
Mcb1, a minichromosome maintenance-binding protein (MCM-BP), is crucial for DNA replication in fission yeast. It ensures proper MCM complex function and nuclear localization, promoting efficient DNA replication origin firing.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- The minichromosome maintenance (MCM) complex is a vital replicative helicase for DNA replication.
- A novel MCM-binding protein (MCM-BP) has been identified, but its function and interaction with MCM complexes are poorly understood.
- The role of MCM-BP is controversial and may differ across organisms.
Purpose of the Study:
- To investigate the function and biological role of the MCM-BP ortholog, Mcb1, in fission yeast.
- To elucidate the mechanisms of Mcb1 interaction with MCM complexes.
- To understand Mcb1's contribution to DNA replication regulation.
Main Methods:
- Isolation and characterization of two temperature-sensitive mcb1 gene mutants (mcb1(ts)).
- Genetic analysis including suppression studies with mcm5(+) multicopy plasmid and synthetic defect analysis with S-phase mutants.
- Analysis of cyclin-dependent kinase modulation and MCM subunit localization.
Main Results:
- Mcb1 interacts with MCM proteins throughout the cell cycle in vivo and with individual MCM subunits in vitro.
- mcb1(ts) mutants show defects in pre-replication complex (pre-RC) formation, reduced Mcm7 loading, and delayed S-phase progression.
- mcb1(ts) mutations cause MCM subunit redistribution to the cytoplasm, dependent on the nuclear export system.
Conclusions:
- Mcb1 plays a critical role in promoting efficient pre-RC formation during DNA replication in fission yeast.
- Mcb1 regulates the MCM complex, ensuring its proper function and nuclear localization.
- These findings clarify the functional role of MCM-BP in eukaryotes.
Related Concept Videos
02:37Restarting Stalled Replication Forks
02:19The Spindle Assembly Checkpoint
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
02:15Condensins
The plant and animal cells contain two types of condensin complexes—condensin I and condensin II. Both complexes have five subunits: two SMC (Structural Maintenance of Chromosomes) subunits, a kleisin subunit, and two HEAT-repeat...
03:01The Replisome
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
03:01The Replisome
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
02:15M-Cdk Drives Transition Into Mitosis
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...