Related Experiment Video

Updated: Aug 12, 2026

Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins
05:35

Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins

Published on: March 3, 2016

PCNA is a cofactor for Cdt1 degradation by CUL4/DDB1-mediated N-terminal ubiquitination

Takeshi Senga1, Umasundari Sivaprasad, Wenge Zhu

  • 1Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia 22908, USA.

The Journal of Biological Chemistry
|January 13, 2006
PubMed

Insights

Cell division cycle 1 (Cdt1) protein degradation is crucial for DNA replication control. Proliferating cell nuclear antigen (PCNA) binding targets Cdt1 for degradation, preventing replication errors.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Cdt1 protein is essential for initiating DNA replication during the G1 phase.
  • Cdt1 activity is regulated in S-phase and after DNA damage through geminin binding and proteasomal degradation.
  • Cyclin-dependent kinase phosphorylation of Cdt1 can promote its degradation via SCF-Skp2, but this pathway is not essential.

Purpose of the Study:

  • To investigate the mechanism of Cdt1 degradation beyond the Cdk2/Skp2 pathway.
  • To identify novel degradation signals and regulators of Cdt1 during S-phase and DNA damage response.

Main Methods:

  • Investigated Cdt1 degradation using biochemical assays.
  • Identified protein interactions involving Cdt1, PCNA, Cul4, and Ddb1.
  • Analyzed N-terminal ubiquitination of Cdt1.

Main Results:

  • Discovered a second degradation signal in the N terminus of Cdt1.
  • This signal is active in S-phase and after DNA damage.
  • Cdt1 degradation depends on interaction with proliferating cell nuclear antigen (PCNA) via a PCNA binding motif.
  • Degradation involves N-terminal ubiquitination and the Cul4-Ddb1 E3 ubiquitin ligase complex.

Conclusions:

  • Proliferating cell nuclear antigen (PCNA) plays a dual role in DNA metabolism: facilitating replication and targeting associated proteins for degradation.
  • PCNA promotes the targeted degradation of Cdt1 in S-phase and after DNA damage.
  • This mechanism ensures proper regulation of DNA replication and prevents genomic instability.

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

Quantitative Detection of DNA-Protein Crosslinks and Their Post-Translational Modifications10:12

Quantitative Detection of DNA-Protein Crosslinks and Their Post-Translational Modifications

Published on: April 21, 2023

Related Concept Videos

DNA Damage can Stall the Cell Cycle02:36

DNA Damage can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
Regulated Protein Degradation02:58

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Inhibition of Cdk Activity02:34

Inhibition 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...
Allosteric Proteins-ATCase01:19

Allosteric Proteins-ATCase

Binding sites linkages can regulate a protein's function.  For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to  N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Anaphase Promoting Complex00:50

Anaphase Promoting Complex

The stepwise destruction of specific proteins is necessary for the progression and completion of the cell cycle. Such proteins are ubiquitinated by ubiquitin ligases and then subsequently destroyed by the proteasome. The SCF (Skp1/Cullin/F-box) and the anaphase-promoting complex (APC) are two important ubiquitin ligases involved in cell cycle progression. While SCF is active throughout the cell cycle, APC gets activated during metaphase to anaphase transition. Cdc20 or Cdh1 binds to APC and...
DNA Damage Can Stall the Cell Cycle02:36

DNA Damage Can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...