The DNAJB5 Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout cell population targeting the human DNAJB5 gene, generating a loss-of-function model for chaperone biology and stress response studies. This polyclonal pool maintains genetic diversity after editing, providing a robust system to investigate protein quality control mechanisms without clonal selection artifacts.
HAP1 is a near-haploid cell line derived from the chronic myeloid leukemia line KBM-7 (male origin), exhibiting adherent, fibroblast-like morphology. Its near-haploid karyotype enables highly efficient CRISPR/Cas9-mediated gene disruption, as single-allele targeting suffices for functional knockout. This feature makes HAP1 a widely adopted model for haploid genetic screening and functional genomics.
DNAJB5 encodes a J-domain co-chaperone that directly interacts with Hsp70 family members, primarily the stress-inducible HSPA1A (Hsp70) and the constitutively expressed HSPA8 (Hsc70), stimulating their ATPase activity. This activation accelerates client-protein processing, promoting proper folding under homeostasis and targeting terminally misfolded substrates for degradation. Upstream, DNAJB5 is transcriptionally regulated by Heat shock factor 1 (HSF1) in response to heat stress, oxidative stress, and heavy-metal exposure. Mechanistically, DNAJB5 couples substrate recognition to ubiquitination by recruiting the E3 ligase CHIP (STUB1), which polyubiquitinates clients destined for the 26S proteasome. BAG family co-chaperones further modulate Hsp70 interaction cycles. Consequently, DNAJB5 knockout disrupts constitutive and stress-inducible proteostasis, impairing cellular stress resistance.
In HAP1 cells, the DNAJB5 knockout provides a clean genetic background to dissect chaperone-dependent pathways without functional redundancy from additional alleles. The near-haploid architecture simplifies phenotypic interpretation, making this model particularly valuable for cancer biology, where proteotoxic stress is elevated, and for investigating protein misfolding disorders and neurodegeneration. The polyclonal format offers a population-level view of stress response dysregulation, minimizing clonal adaptation biases.
Researchers can apply these cells in functional genomics screens, chaperone biology studies, stress response assays, and drug sensitivity screening. Representative experimental readouts include Western blotting and RT-qPCR for target and pathway analysis, immunofluorescence for subcellular localization, Hsp70 ATPase activity measurements, protein aggregation assays, and cell viability tests under heat shock. This model is well-suited to identify compounds exploiting proteostasis vulnerabilities in cancer. For further technical information, please contact Ascent Research.
