The APOBEC3B Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout cell population originating from the HAP1 near-haploid human cell line. This product provides a loss-of-function model for the APOBEC3B gene, which encodes a cytidine deaminase critical for cancer mutagenesis and antiviral innate immunity. By disrupting APOBEC3B expression, researchers can investigate its role in generating C-to-U deamination in single-stranded DNA, promoting hypermutation and genomic instability. The polyclonal knockout pool allows population-based functional studies, minimizing clonal artifacts and ensuring robust assay performance.
HAP1 is a chronic myeloid leukemia-derived, near-haploid fibroblast-like cell line established from the KBM-7 line. Its near-haploid karyotype simplifies genetic analyses, making it a favored platform for CRISPR-based knockout screens and functional validation. These adherent cells maintain active DNA damage response and immune signaling pathways, making them well-suited for studying APOBEC3B-driven processes. The haploid genome facilitates clear phenotypic interpretation without interference from allelic compensation.
APOBEC3B acts as an ssDNA cytidine deaminase, converting cytosine to uracil, which generates abasic sites and DNA double-strand breaks. Its transcription is induced by interferons through STAT1, and by NF-??B and AP-1 upon inflammatory stimulation. At replication forks, APOBEC3B interacts with PCNA and replication protein A, while its mutagenic effects are modulated by REV1 and UNG. The resultant DNA damage activates ATR/ATM kinases, leading to CHK1/CHK2-mediated p53 stabilization, triggering cell cycle arrest or apoptosis. This pathway underlies both APOBEC3B’s role in tumor evolution and its antiviral function against retroviruses and retrotransposons.
In the near-haploid HAP1 background, APOBEC3B knockout enables direct measurement of its impact on endogenous mutation signatures and DNA damage checkpoint activation. Without a second allele to mask effects, loss of APOBEC3B clearly reveals its contribution to C-to-T mutations and TP53 mutagenesis. The model is particularly useful for dissecting interactions between APOBEC3B activity and DNA repair pathways, such as base excision repair and nucleotide excision repair, and for assessing how APOBEC3B-driven genetic diversification contributes to drug resistance. Compatibility with high-throughput screening further enables genome-wide modifier or chemical library screens.
Typical applications include cancer mutagenesis mechanism studies using whole-genome sequencing for mutation signature analysis, as well as dual-fluorescence deaminase reporter assays and comet assays for quantifying DNA damage. These knockout cells support flow cytometric cell cycle profiling, viability and drug sensitivity testing, and CRISPR gRNA validation. They also serve in antiviral immunity research and tumor drug resistance investigations. For additional details or custom assay development, please contact Ascent Research.
