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Related Concept Videos

Restarting Stalled Replication Forks02:37

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...
Restarting Stalled Replication Forks02:37

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...
M-Cdk Drives Transition Into Mitosis02:15

M-Cdk Drives Transition Into Mitosis

Checkpoints throughout the cell cycle serve as safeguards and gatekeepers, allowing the cell cycle to progress in favorable conditions and slow or halt it in problematic ones. This regulation is known as the cell cycle control system.
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...
M-Cdk Drives Transition Into Mitosis02:15

M-Cdk Drives Transition Into Mitosis

Checkpoints throughout the cell cycle serve as safeguards and gatekeepers, allowing the cell cycle to progress in favorable conditions and slow or halt it in problematic ones. This regulation is known as the cell cycle control system.
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...
Separation of Sister Chromatids02:17

Separation of Sister Chromatids

At the transition from prophase to metaphase, there is a reduction in cohesion along the chromosomal arms, resulting in the resolution of sister chromatids. However, residual cohesin connections remain to hold the sister chromatids together until the transition from metaphase to anaphase. The residual connection prevents any premature separation of sister chromatids, blocking the risks of aneuploidy within the daughter cells.
At the onset of anaphase, separase, a proteolytic enzyme, is...
The Spindle Assembly Checkpoint02:19

The Spindle Assembly Checkpoint

The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
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...

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Updated: Jun 2, 2026

Combining Mitotic Cell Synchronization and High Resolution Confocal Microscopy to Study the Role of Multifunctional Cell Cycle Proteins During Mitosis
08:33

Combining Mitotic Cell Synchronization and High Resolution Confocal Microscopy to Study the Role of Multifunctional Cell Cycle Proteins During Mitosis

Published on: December 5, 2017

Timeless links replication termination to mitotic kinase activation.

Jayaraju Dheekollu1, Andreas Wiedmer, James Hayden

  • 1The Wistar Institute, Philadelphia, Pennsylvania, United States of America.

Plos One
|May 17, 2011
PubMed
Summary

Human Timeless protein (Tim) coordinates DNA replication termination with mitotic entry. Tim depletion causes mitotic defects and delays kinase activity, revealing its crucial role in cell cycle progression.

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Last Updated: Jun 2, 2026

Combining Mitotic Cell Synchronization and High Resolution Confocal Microscopy to Study the Role of Multifunctional Cell Cycle Proteins During Mitosis
08:33

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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
12:26

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Published on: May 3, 2018

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • The coordination between DNA replication termination and mitosis progression is not fully understood.
  • Human Timeless protein (Tim) is involved in replication fork stability and checkpoint control.

Purpose of the Study:

  • To investigate the role of human Timeless protein (Tim) in coordinating DNA replication termination with mitotic entry.
  • To elucidate the molecular mechanisms by which Tim influences mitotic progression and kinase activity.

Main Methods:

  • Co-immunoprecipitation to identify proteins interacting with Tim.
  • In vitro kinase assays to assess Tim's effect on mitotic kinases.
  • siRNA-mediated Tim depletion to observe mitotic phenotypes.
  • Immunofluorescence microscopy to analyze protein localization and mitotic structures.

Main Results:

  • Human Tim was found in a complex with mitotic kinases CDK1, Auroras A and B, and Plk1.
  • Tim depletion led to loss of sister-chromatid cohesion, defective spindle architecture, and failure to exit mitosis.
  • Tim depletion delayed mitotic kinase activity and reduced histone H3 S10 phosphorylation.
  • Tim is essential for Plk1 recruitment to centromeres and formation of catenated DNA structures.

Conclusions:

  • Human Timeless protein (Tim) plays a critical role in coordinating DNA replication termination with mitotic kinase activation.
  • Tim is a key regulator of mitotic entry, spindle assembly, and sister-chromatid cohesion.
  • These findings highlight Tim's function as a molecular link between DNA replication and mitosis.