Related Experiment Video
Updated: May 20, 2026
12:26
Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
F-box protein specificity for g1 cyclins is dictated by subcellular localization
Benjamin D Landry1, John P Doyle, David P Toczyski
1Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA, USA.
Plos Genetics
|July 31, 2012
Summary
Two SCF ubiquitin ligases, SCF(Cdc4) and SCF(Grr1), redundantly degrade the G1 cyclin Cln3 in budding yeast. Subcellular localization contributes to substrate specificity, revealing shared targets and redundancy between these ligases.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- G1 cyclins regulate cell size and entry into mitosis.
- Cln3 is a key G1 cyclin in budding yeast, crucial for cell cycle progression.
- Mechanisms controlling Cln3 degradation are not fully understood.
Purpose of the Study:
- Investigate the mechanisms governing Cln3 degradation.
- Identify the ubiquitin ligases responsible for Cln3 targeting.
- Determine the role of F-box proteins (FBPs) Cdc4 and Grr1 in Cln3 regulation.
Main Methods:
- Yeast genetics and molecular biology techniques.
- Analysis of protein-protein interactions using cell extracts.
- In vivo degradation assays.
- Subcellular localization studies.
Main Results:
- SCF(Cdc4) and SCF(Grr1) redundantly target Cln3 for degradation.
- Cdc4 and Grr1 bind to all three G1 cyclins, but Cln3 is uniquely targeted redundantly in vivo.
- Nuclear localization of Cln3 contributes to its redundant targeting.
- Cln2 is cytoplasmic and exclusively targeted by Grr1, though Cdc4 can target it under specific conditions.
- grr1Δ cdc4-1 mutants exhibit synergistic growth defects, suggesting shared substrates.
Conclusions:
- Structurally distinct FBPs, Cdc4 and Grr1, can target overlapping substrates.
- Subcellular localization is a key determinant of in vivo substrate specificity.
- Cdc4 and Grr1 exhibit partial functional redundancy essential for cell proliferation and viability.
- These findings reveal novel insights into cell cycle control and ubiquitin-mediated protein degradation.
Related Concept Videos
02:39Positive 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.
01:45Positive Regulator Molecules
To consistently produce healthy cells, the cell cycle—the process that generates daughter cells—must be precisely regulated.
01:57Protein Complexes with Interchangeable Parts
Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
02:34Inhibition of Cdk Activity
The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...
02:15M-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...
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...
01:28The Cell Cycle Control System
The cell cycle regulation directs how a cell proceeds from one phase to the next and begins mitosis. The cell cycle control system includes intracellular regulatory molecules and external triggers. They provide "stop" or "advance" signals and operate at specific cell cycle stages termed checkpoints to ensure that a particular process is completed before the cell advances to the next phase.
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...