RAD50 and DNA Damage Response

Mon, 02/17/2014 - 11:26

DNA repair protein RAD50 is a component of the MRN complex (Mre11-RAD50-Nbs1) responsible for DNA double strand break (DSB) repair. DSBs are caused by ionizing radiation, certain chemotherapy drugs, metabolic reactive oxygen species (ROS), replication errors, and programmed enzymatic activity during meiosis or V(D)J recombination.  If left unrepaired, DSBs generate extremely problematic chromosomal translocations, aneuploidy, and carcinogenesis. As a DSB sensor, RAD50 detects and signals the presence of DSBs. RAD50 is a co-activator for DSB-induced cell cycle checkpoint signaling, and operates as a repair-effector in two competing repair pathways: homologous recombination (HR) as well as non-homologous end-joining (NHEJ). The MRN complex associates with and helps maintain the telomeres found at the ends of linear chromosomes. RAD50 specifically binds DNA ends allowing them to be held in close proximity as it facilitates the search for short or long sequence homology regions in the recombining DNA templates. RAD50 also stimulates DNA ligase activity and/or restricts activity of the MRE11A nuclease to prevent nucleolytic degradation. RAD50 antibody was employed by Stewart’s group in silencing experiments to confirm the crucial role of mediator of DNA damage checkpoint protein 1 (MDC1) in transducing histone H2A variant H2AX-mediated signaling in response to ionizing radiation DNA damage (1). Furuta, et al. examined the role of phosphorylated H2AX foci in HCT116 human carcinoma cells exposed to topo I inhibitors through immunoblotting and immunofluorescence experiments with the RAD50 antibody to better understand the convergent cellular response to DSBs from divergent causes (2).

Western Blot: RAD50 Antibody Western Blot: RAD50 Antibody

In the aging arena, RAD50 antibody allowed the investigation of the linkage between the recessive genetic disorders Werner’s syndrome and Nijmegen breakage syndrome (3). Use of RAD50 antibody in immunoprecipitations allowed researchers to functionally link the two genetic diseases through partially overlapping phenotypes in an Nbs1 common mechanism. Additionally, Rink’s group used the RAD50 antibody to further characterize the phosphorylated states of Nbs1 and its associated proteins in BCR/ABL-positive leukemia cells (4). Adenoviral studies with the RAD50 antibody were done to better understand the temporal regulation of the MRN complex during infection, and data suggests that input viral DNA, without new viral DNA accumulation, is sufficient to induce DNA damage (5).

  1. PMID: 12607005
  2. PMID: 12660252
  3. PMID: 15026416
  4. PMID: 17431132
  5. PMID: 19244322

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