Related Experiment Video

Updated: Apr 2, 2026

Oligopeptide Competition Assay for Phosphorylation Site Determination
09:16

Oligopeptide Competition Assay for Phosphorylation Site Determination

Published on: May 18, 2017

9.0K

Identification of cell cycle-regulated phosphorylation sites on nuclear lamin C

G E Ward1, M W Kirschner

  • 1Department of Biochemistry and Biophysics, University of California, San Francisco 94143.

Cell
|May 18, 1990
PubMed

Insights

Maturation-promoting factor (MPF) triggers nuclear envelope breakdown during mitosis by phosphorylating nuclear lamins. This phosphorylation leads to lamin filament disassembly, with S6 kinase II identified as a key enzyme in this process.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitosis involves the breakdown of the nuclear envelope, a process regulated by Maturation-Promoting Factor (MPF).
  • Nuclear lamins form a structural network supporting the nuclear envelope and are known targets during cell division.

Purpose of the Study:

  • To investigate the mechanism by which MPF induces nuclear lamin disassembly and nuclear envelope breakdown.
  • To identify specific phosphorylation sites on nuclear lamins and the kinases involved.

Main Methods:

  • Utilized frog egg extract to study the interphase-to-mitosis transition induced by MPF addition.
  • Employed bacterially expressed human nuclear lamin C, assembled into filaments in vitro.
  • Analyzed phosphorylation sites on lamins using sequencing techniques in the presence and absence of MPF.

Main Results:

  • MPF induced increased phosphorylation of nuclear lamin C filaments at specific sites within the frog egg extract.
  • Lamin filament disassembly was observed concurrently with increased phosphorylation.
  • Identified specific amino acid sequences of phosphorylated sites, suggesting multiple kinase activities.
  • S6 kinase II was identified as a potential key kinase responsible for lamin phosphorylation.

Conclusions:

  • MPF-mediated phosphorylation is a critical step in nuclear lamin disassembly and nuclear envelope breakdown during mitosis.
  • The findings highlight the role of specific kinases, including S6 kinase II, in regulating nuclear structure dynamics during cell division.

More Related Videos

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay12:26

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

Published on: May 3, 2018

19.5K
Characterization at the Molecular Level using Robust Biochemical Approaches of a New Kinase Protein11:23

Characterization at the Molecular Level using Robust Biochemical Approaches of a New Kinase Protein

Published on: June 30, 2019

6.8K

Related Concept Videos

Positive Regulator Molecules01:45

Positive Regulator Molecules

To consistently produce healthy cells, the cell cycle—the process that generates daughter cells—must be precisely regulated.
137.2K
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
15.6K
Positive Regulator Molecules02:39

Positive Regulator Molecules

Mitotic cell division results in daughter cells that exactly resemble the parent cell. However, errors in the DNA replication or distribution of genetic material may lead to genetic mutations that may be passed down to every new cell formed from the resulting abnormal cell. Propagation of such mutant cells is restricted through checkpoint mechanisms present at different stages of the cell cycle. These checkpoints involve regulator molecules that either promote or demote cell cycle events.
7.1K
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...
6.8K
Disassembly of Intermediate Filaments01:35

Disassembly of Intermediate Filaments

Intermediate filaments (IFs) do not undergo spontaneous disassembly. Enzymes, kinases, and phosphatases add and remove phosphates from specific sites to regulate their disassembly. The IF concentration in the cytoplasm also regulates the disassembly. If the concentration crosses a threshold, it activates the protein kinases in the vicinity, allowing the phosphorylation of IFs.
Keratin proteins, found at the cell periphery near cell junctions, undergo a cycle of assembly and disassembly. In Type...
2.8K
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
9.2K