The HSPA4L Knockout HAP1 Polyclonal Cells product provides a CRISPR/Cas9-edited polyclonal population of HAP1 cells with targeted disruption of the HSPA4L gene. This polyclonal knockout pool enables loss-of-function studies without clonal selection, retaining genetic heterogeneity. The gene disruption eliminates functional HSPA4L, offering a model to study chaperone deficiency.
HAP1 is a near-haploid human cell line originally isolated from a male patient with chronic myeloid leukemia. It exhibits fibroblast-like adherent morphology and retains a single copy of most chromosomes, except for a small disomic region on chromosome 15. This genetic simplicity minimizes functional redundancy and off-target effects, making HAP1 an ideal host for CRISPR-based knockout experiments and functional genomic screens. Its derivation from a hematopoietic malignancy further positions it as a relevant model for studying cancer cell stress responses.
HSPA4L encodes a member of the heat shock protein 70 (HSP70) family that functions as an ATP-dependent molecular chaperone. Under basal and stress conditions, it binds to nascent polypeptides and stress-denatured proteins, preventing aggregation and facilitating proper folding. The HSPA4L promoter contains heat shock elements that are recognized by the transcription factor HSF1, leading to robust upregulation during heat shock, oxidative stress, and cytokine stimulation. In the chaperone cycle, HSPA4L collaborates with HSP40 co-chaperones such as DNAJB1, which stimulate its ATPase activity, and with the HOP adaptor protein that mediates transfer of substrates to HSP90. Additionally, the E3 ubiquitin ligase STUB1/CHIP interacts with HSPA4L to target chronically misfolded proteins for proteasomal degradation. Disruption of HSPA4L therefore impairs both protein folding and the triage of damaged proteins, perturbing cellular proteostasis and potentially sensitizing cells to stress-induced apoptosis, reflected in altered expression of downstream stress genes like HSPA1A.
In the context of HAP1 cells, the HSPA4L knockout model takes advantage of the near-haploid genome to achieve a clean loss-of-function state, eliminating residual activity from a second allele. This system is particularly suited for interrogating chaperone networks in a cancer cell background, as leukemia cells often rely on elevated chaperone expression for survival under oncogenic stress. Consequently, HSPA4L disruption may uncover vulnerabilities that can be exploited for therapeutic targeting. Moreover, the male origin of HAP1 and the proposed involvement of HSPA4L in spermatogenesis provide an opportunity to investigate germ cell-related functions, although the somatic nature of HAP1 imposes certain limitations.
Typical research applications include mechanistic dissection of the HSP70 chaperone system, quantitative assessment of cellular stress tolerance, and synthetic lethality screening in cancer models. To validate knockout, researchers can perform western blotting for HSPA4L and monitor stress-inducible proteins such as HSPA1A by RT-qPCR. Functional assays, including cell viability measurements under heat shock or proteasome inhibition, directly probe the impact of HSPA4L loss on stress survival. Protein aggregation assays using fluorescent dyes or detergent solubility tests quantify proteostasis capacity. Flow cytometric analysis of apoptosis markers (e.g., annexin V/PI staining) reveals the propensity for stress-induced cell death. Immunofluorescence microscopy for stress granule markers (such as G3BP1) enables visualization of altered RNA granule dynamics. For technical assistance or to discuss custom applications, please contact Ascent Research.
