The DNA Damage Response Pathway

The DNA Damage Response detects DNA lesions caused by replication errors or external agents and mobilizes proteins for repair. DNA damage response proteins include:

  • DNA-PK – Senses double-stranded breaks (DSBs)
  • PARP1 – Binds to DSBs and forms poly-ADP-ribose (PAR)
  • PARG – Removes PAR following DNA repair
  • POLQ - DNA-modifying enzyme in DSB repair
  • WRN – DNA-modifying enzyme in DSB repair

What Occurs During a DNA Damage Response?

During the DNA damage response (DDR) pathway, a cascade of signaling events occurs that include DNA damage detection, cell cycle arrest to facilitate repair, and activation of DNA repair pathways (homologous recombination, non-homologous end joining, etc.). The DNA lesion is either repaired or cell apoptosis occurs if the damage is irreparable.

Certain DNA damage response proteins are responsible for detection of DNA damage and facilitation of downstream DNA repair mechanisms. Ataxia-Telangiectasia Mutated (ATM) activates in response to DNA double-stranded breaks (DSBs) and phosphorylates downstream targets to initiate DNA damage repair. DNA-dependent protein kinase (DNA-PK) is also involved in recognition of DNA DSBs and initiates repair mechanisms. ATM and Rad3-related (ATR) activates in response to single-stranded breaks and stalled replication forks, playing an important role in the response to DNA replication stress.

Various sensor, signaling, and effector proteins attend to different kinds of DNA damage. Single-strand breaks (SSBs) in DNA are mended by either base excision repair (BER), nucleotide excision repair (NER), or mismatch repair (MMR). Double stranded breaks (DSBs), the most serious type of DNA damage, are mostly remedied by homologous recombination (HR) or non-homologous end-joining (NHEF).

DNA Damage Response Proteins

The DNA Damage Response (DDR) & Innate Immunity

There is extensive crosstalk between the DDR pathways and innate immune pathways. In this illustration, we highlight these interconnections between the pathways. Here, DNA damaging agents induce a DDR in the tumor cell's nucleus. dsDNA forms in the cytoplasm from leaked DNA from the nucleus or micronuclei. Detection of the dsDNA by PRRs is accompanied by an innate immune response, inducing Type I IFNs and pro-inflammatory cytokines. Extracellularly, adenosine (ADO) and cGAMP regulate innate immune responses; the levels of both are controlled by ectonucleotidases. 

In our latest eBook, we detail connections between DDR & innate immunity pathways, and describe Transcreener Assays and Assay Systems for key therapeutic targets. 

DNA Damage Response and Innate Immunity Preview
DNA Damage Response & Innate Immunity Pathway

Synthetic Lethality and Cancer Therapeutics

Synthetic lethality is when the occurrence of two genes together is lethal,  but the occurrence of those genes individually is not lethal. Using the synthetic lethal strategy for anti-cancer drug therapeutics has shown tremendous promise: tumors with genetic deficiency in the DDR are selectively killed with a drug targeting a second DDR protein. The use of PARP inhibitors for ovarian tumors with BRCA-1 mutations was the first clinical example of this approach. More recently, POLQ was found to be synthetically lethal in tumors with common BRCA and ATM mutations, providing an alternative therapeutic strategy for PARPi-resistant tumors.

DNA Damage Response Assays

DNA damage response assays play a crucial role in investigating the DNA damage response proteins, and developing small molecule modulators for the pathway that show great potential as disease therapeutics. Here at BellBrook, we develop and commercialize ready-made assays for DDR proteins that will accelerate researchers' efforts to discover these modulators.

We focus on creating complete assay solutions for tougher enzyme targets that are difficult to source enzyme or develop an assay for so you can focus on optimizing your lead molecules. We also offer lead discovery and assay development services for those who do not want to bring an assay in-house. With our services, you will directly collaborate with our scientists who are experts in the DDR pathway. Our services offer quick turnaround times, custom assay conditions, and extensive expertise.

Assay Solutions for Your Toughest DDR Targets

Easy-to-Use Assay Symbol

Easy-to-Use & HTS-Ready

A simple assay protocol that is ready to scale up for HTS (Z' > 0.7).

Direct Detection of ADP Antibody

Direct Detection

Many of our assays offer direct nucleotide detection, which reduces the risk of false positives or missing a hit.

Transcreener Sensitive Technology

Ultra-Sensitive Assays

The unparalleled sensitivity of the assay technology allows high-throughput screening with reduced enzyme usage.

Outstanding Assay Reagent Stability Symbol

Great Reagent Stability

Stability at room temperature for at least 8 hours ensures data quality doesn't suffer in a large, automated screen.

Contact a BellBrook Scientist Today

Interested in purchasing an assay or advancing your program with our drug discovery services? Have questions about the assay technology? Contact a BellBrook scientist today to see how we can help accelerate your discovery.


Gupta, P, et al. (2022) Enigmatic role of WRN-RECQL helicase in DNA repair and its implications in cancer. Journal of Translational Genetics and Genomics, 6(2): 147-56. http://dx.doi.org/10.20517/jtgg.2021.60 

James, D. I. et al. (2016) First-in-Class Chemical Probes against Poly(ADP-ribose) Glycohydrolase (PARG) Inhibit DNA Repair with Differential Pharmacology to Olaparib. ACS Chemical Biology, 11 (11), 3179-3190. https://doi.org/10.1021/acschembio.6b00609

Molinaro, C. et al. (2021) Proteins from the DNA Damage Response: Regulation, Dysfunction, and Anticancer Strategies. Cancers, 13(15), 3819. https://doi.org/10.3390/cancers13153819

Mullard, A. (2022) What’s next for the synthetic lethality drug discovery engine? Nature Reviews Drug Discovery, 1474-1784 (online). https://doi.org/10.1038/d41573-022-00107-0

Nijman, S. (2011) Synthetic lethality: General principles, utility and detection using genetic screens in human cells. FEBS Lett., 585(1):1-6. https://doi.org/10.1016/j.febslet.2010.11.024

Pascal, J.M. (2019) The comings and goings of PARP-1 in response to DNA damage. DNA Repair, 71:177-182. https://doi.org/10.1016/j.dnarep.2018.08.022

Taffoni, C. et al. (2021) Nucleic Acid Immunity and DNA Damage Response: New Friends and Old Foes. Frontiers in Immunology, 12, 660560. https://doi.org/10.3389/fimmu.2021.660560

Zahn, K.E. and Jensen, R.B. (2021) Polymerase θ Coordinates Multiple Intrinsic Enzymatic Activities during DNA Repair. Genes, 12(9):1310. https://doi.org/10.3390/genes12091310

Zatreanu, D. et al. (2021) POLQ inhibitors elicit BRCA-gene synthetic lethality and target PARP inhibitor resistance. Nature Communications, 12:3636. https://doi.org/10.1038/s41467-021-23463-8