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Updated: May 2, 2026

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

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Assessing kinetics from fixed cells reveals activation of the mitotic entry network at the S/G2 transition

Karen Akopyan1, Helena Silva Cascales1, Elvira Hukasova1

  • 1Department of Cell and Molecular Biology, Karolinska Institutet, von Eulers väg 3, 171 77 Stockholm, Sweden.

Molecular Cell
|March 4, 2014
PubMed

Insights

Mitotic entry is triggered by DNA replication completion, not G2 phase protein accumulation. This study reveals the cell cycle timing of mitotic entry signaling networks.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The cell cycle requires DNA replication (S phase) before cell division (mitosis).
  • Accumulation of mitotic inducers during G2 phase typically triggers entry into mitosis.
  • The precise timing and activation mechanisms of the mitotic entry signaling network remain unclear.

Purpose of the Study:

  • To investigate the kinetics of mitotic entry signaling network activation relative to cell cycle events.
  • To determine if mitotic entry depends on protein accumulation during the G2 phase.
  • To provide quantitative data for mathematical modeling of the human cell cycle.

Main Methods:

  • Development of a novel system to minimize cell-cell variation and enhance fluorescence quantification accuracy in single cells.
  • Utilizing immunofluorescence of endogenous marker proteins to assess signaling kinetics in fixed cells.
  • Analyzing the temporal occurrence of mitotic phosphorylations in relation to S phase completion.

Main Results:

  • Mitotic phosphorylations initiate precisely at the completion of S phase.
  • Activation of the mitotic entry network is independent of protein accumulation throughout the G2 phase.
  • Demonstrated a direct link between S phase completion and the initiation of mitotic entry.

Conclusions:

  • Mitotic entry is tightly linked to the completion of DNA replication, not solely dependent on G2 phase progression.
  • The developed single-cell analysis system offers high accuracy for studying cell cycle dynamics.
  • Findings provide a quantitative framework for understanding and modeling human cell cycle control.

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