Related Experiment Video

Updated: Sep 21, 2026

In Vivo Detection and Analysis of Rb Protein SUMOylation in Human Cells
09:40

In Vivo Detection and Analysis of Rb Protein SUMOylation in Human Cells

Published on: November 2, 2017

The Dun1 checkpoint kinase phosphorylates and regulates the ribonucleotide reductase inhibitor Sml1

Xiaolan Zhao1, Rodney Rothstein

  • 1Department of Genetics and Development, Columbia University, College of Physicians and Surgeons, 701 West 168th Street, New York, NY 10032-2704, USA.

Proceedings of the National Academy of Sciences of the United States of America
|March 21, 2002
PubMed

Insights

The Dun1 kinase phosphorylates and degrades the Sml1 protein, which is crucial for DNA replication and repair during cell cycle checkpoints. This regulation ensures genomic stability and prevents cancer.

Area of Science:

  • Cellular biology
  • Molecular genetics
  • Biochemistry

Background:

  • Cell cycle checkpoints are vital for maintaining genomic stability and preventing cancer.
  • Ribonucleotide reductase (RNR) is essential for DNA synthesis and is regulated by checkpoint pathways.
  • The RNR inhibitor Sml1 is regulated by Mec1/Rad53, but the mechanism remains unclear.

Purpose of the Study:

  • To elucidate the molecular mechanism by which Mec1/Rad53 regulate Sml1.
  • To investigate the role of Dun1 kinase in Sml1 regulation.
  • To understand the impact of Dun1-mediated Sml1 regulation on DNA replication and repair.

Main Methods:

  • Genetic analysis of yeast strains with mutations in Dun1 and Sml1.
  • Co-immunoprecipitation to assess protein interactions.
  • In vitro kinase assays to determine Dun1's enzymatic activity on Sml1.

Main Results:

  • Dun1 genetically and physically interacts with Sml1.
  • Absence of Dun1 leads to Sml1 accumulation, delayed DNA replication, and sensitivity to DNA damage.
  • Dun1 directly phosphorylates Sml1 in vitro, and phospho-Sml1 is absent in dun1Delta cells.

Conclusions:

  • Dun1 kinase is the final effector in the Mec1/Rad53 pathway for Sml1 degradation.
  • Dun1-mediated Sml1 regulation is critical for DNA repair, replication, and genomic integrity.
  • This study reveals a key regulatory step in the DNA damage response pathway.

More Related Videos

Assessment of Global DNA Double-Strand End Resection using BrdU-DNA Labeling coupled with Cell Cycle Discrimination Imaging06:44

Assessment of Global DNA Double-Strand End Resection using BrdU-DNA Labeling coupled with Cell Cycle Discrimination Imaging

Published on: April 28, 2021

Comparative Strategies for Ubiquitination Detection in Mammalian Cell Lysates Using SMAD2/SMURF2 as a Model09:00

Comparative Strategies for Ubiquitination Detection in Mammalian Cell Lysates Using SMAD2/SMURF2 as a Model

Published on: April 17, 2026

Related Concept Videos

Negative Regulator Molecules01:23

Negative Regulator Molecules

Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
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...
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...
Regulation of the Unfolded Protein Response01:31

Regulation of the Unfolded Protein Response

Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...
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...
TGF - β Signaling Pathway01:16

TGF - β Signaling Pathway

The TGF-β signaling pathway regulates cell growth, differentiation, adhesion, motility, and development. TGF-β ligands that induce TGF-β signaling are synthesized in their latent form. Several proteases or cell surface receptors such as integrins act upon the latent form, releasing the active ligand. There are three types of mammalian TGF-βs: (TGF-β1, TGF-β2, and TGF-β3) that bind as homodimers or heterodimers to TGF-β receptors. The TGF-β receptors are of three kinds RI, RII, and RIII. The RI...