Related Experiment Video

Updated: Aug 29, 2026

Visualization of DNA Repair Proteins Interaction by Immunofluorescence
07:55

Visualization of DNA Repair Proteins Interaction by Immunofluorescence

Published on: June 26, 2020

53BP1 and NFBD1/MDC1-Nbs1 function in parallel interacting pathways activating ataxia-telangiectasia mutated (ATM) in

Tamara A Mochan1, Monica Venere, Richard A DiTullio

  • 1The Wistar Institute, Philadelphia, Pennsylvania 19104-4268, USA.

Cancer Research
|December 26, 2003
PubMed

Insights

53BP1 and NFBD1/MDC1 are key mediators of DNA double-strand break (DSB) signaling. Suppressing these proteins reveals distinct pathways involving ATM activation, crucial for DNA repair.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Genetics

Background:

  • 53BP1 and NFBD1/MDC1 are recruited to DNA double-strand breaks (DSBs).
  • They are hypothesized to act as mediators of DNA DSB signaling downstream of ATM.
  • Their precise roles in ATM activation and signaling remain to be fully elucidated.

Purpose of the Study:

  • To investigate the roles of 53BP1 and NFBD1/MDC1 in DNA double-strand break (DSB) signaling.
  • To determine if these proteins function as mediators of ATM activation.
  • To elucidate the pathways through which DSBs activate ATM.

Main Methods:

  • Small interfering RNA (siRNA) was used to suppress the expression of 53BP1 and NFBD1/MDC1.
  • ATM autophosphorylation at Ser1981 was monitored as a marker for ATM activation.
  • Recruitment of NFBD1/MDC1 and Nbs1 to DSB sites was assessed in cells with wild-type and mutant Nbs1.

Main Results:

  • Suppression of NFBD1/MDC1 led to decreased ATM activation and phosphorylation of its substrates, similar to cells with defective Nbs1.
  • In cells with wild-type Nbs1, 53BP1 suppression did not affect ATM activation but increased NFBD1/MDC1 and Nbs1 recruitment to DSBs.
  • In cells with mutant Nbs1, 53BP1 suppression resulted in decreased ATM activation and substrate phosphorylation.

Conclusions:

  • DNA double-strand breaks activate ATM through at least two independent pathways.
  • One pathway involves 53BP1, and the other involves NFBD1/MDC1 in complex with Nbs1.
  • These findings clarify the roles of 53BP1 and NFBD1/MDC1 as critical mediators in DSB signaling and ATM activation.

More Related Videos

Visualizing the DNA Damage Response in Purkinje Cells Using Cerebellar Organotypic Cultures08:41

Visualizing the DNA Damage Response in Purkinje Cells Using Cerebellar Organotypic Cultures

Published on: December 27, 2024

Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins10:24

Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins

Published on: September 28, 2012

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...
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...
Long-patch Base Excision Repair01:02

Long-patch Base Excision Repair

Since the discovery of the two BER pathways, there has been a debate about how a cell chooses one pathway over the other and the factors determining this selection. Numerous in vitro experiments have pointed out multiple determinants for the sub-pathway selection. These are:
Nucleotide Excision Repair01:38

Nucleotide Excision Repair

DNA Distortion and Damage
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
Nucleotide Excision Repair01:46

Nucleotide Excision Repair

Exposure to mutagens can damage DNA and result in bulky lesions that distort the double-helix structure or impede proper transcription. Damaged DNA can be detected and repaired in a process called nucleotide excision repair (NER). NER employs a set of specialized proteins that first scan DNA to detect a damaged region. Next, NER proteins separate the strands and excise the damaged area. Finally, they coordinate the replacement with new, matching nucleotides.DNA distortion and damageCells are...
Restarting Stalled Replication Forks02:37

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...