The NBN Knockout Raji Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout cell population derived from the Raji B lymphocyte cell line, engineered to disrupt the NBN gene encoding nibrin. This product provides a heterogeneous pool of cells with targeted disruption of the NBN locus, enabling loss-of-function studies of the MRN complex in a hematopoietic background. The polyclonal format circumvents clonal selection artifacts and allows for assessment of population-level responses to DNA damage, reflecting the diversity inherent in tumor cell populations.
Raji cells are an Epstein-Barr virus (EBV)-transformed human Burkitt’s lymphoma B lymphocyte line, widely utilized as a model for B-cell malignancies and immune cell function. These cells retain key features of mature B cells, including surface immunoglobulin expression, antigen presentation capacity, and active signal transduction pathways relevant to lymphomagenesis. Their transformed status confers robust proliferation and genetic stability in culture, making them tractable for high-throughput screening and mechanistic dissection of oncogenic signaling. The malignant B-cell context of Raji cells is particularly relevant for exploring connections between DNA repair deficiencies and lymphomagenesis, as NBN mutations are associated with Nijmegen breakage syndrome, a disorder predisposing to lymphoma.
NBN encodes nibrin, a core component of the MRN complex (MRE11?CRAD50?CNBN), which functions as the primary sensor of DNA double-strand breaks (DSBs). Upon DSB induction, the MRN complex rapidly localizes to damage sites, where it activates the ATM kinase by promoting its autophosphorylation and monomerization. Activated ATM phosphorylates a multitude of downstream effectors, including CHK2, p53, SMC1, and H2AX, initiating cell cycle checkpoints and DNA repair pathways. Nibrin directly interacts with MRE11, RAD50, ATM, ??H2AX, MDC1, and BRCA1, serving as an adaptor that recruits ATM and repair factors to chromatin flanking breaks. Disruption of NBN therefore uncouples DSB recognition from ATM signaling, abrogating phosphorylation of CHK2 and p53, and impairing both homologous recombination and non-homologous end joining. Consequently, NBN knockout cells exhibit defective G1/S and intra-S checkpoints, increased radiosensitivity, and heightened genomic instability.
In the Raji B-lymphocyte background, loss of NBN function profoundly compromises the DNA damage response, a pathway frequently dysregulated in B-cell lymphomas. As Raji cells are EBV-transformed and harbor additional genomic alterations, NBN knockout exacerbates replication stress and chromosomal aberrations, providing a syngeneic model to study synthetic lethal interactions and oncogene-induced DNA damage. This model is particularly suited to investigate how impaired ATM signaling cooperates with EBV latency programs to drive genomic instability and clonal evolution. Moreover, the absence of nibrin in B cells mirrors aspects of Nijmegen breakage syndrome-associated immunodeficiency and tumor predisposition, enabling dissection of tissue-specific roles of the MRN complex in lymphocyte development and transformation.
Researchers can utilize these polyclonal knockout cells in a broad range of assays to probe DNA repair kinetics and drug responses. Western blotting for NBN, phospho-ATM, and ??H2AX confirms target disruption and pathway inactivation, while immunofluorescence for ??H2AX foci provides quantitative readouts of DSB accumulation. Flow cytometry-based cell cycle and apoptosis analyses, combined with drug sensitivity assays using etoposide or cisplatin, reveal chemosensitization profiles. Comet assays and colony formation tests further assess genomic instability and clonogenic survival. Additionally, RT-qPCR for DNA repair genes can track transcriptional adaptations. These applications make the cells a versatile tool for DNA damage response studies, cancer biology, and B-cell lymphoma research. For additional details or custom requirements, please contact Ascent Research.
