The CCNT1 Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout population derived from human near-haploid HAP1 cells, engineered for disruption of the CCNT1 gene encoding Cyclin T1. This loss-of-function model allows robust interrogation of Cyclin T1-dependent transcriptional regulation and signaling in a genetically tractable background. The polyclonal format reduces clonal bias and is ideal for pooled functional screens and drug-response profiling.
HAP1 is a near-haploid chronic myeloid leukemia (CML) cell line originating from KBM-7, which harbors the BCR-ABL oncogenic fusion. Its haploid genome simplifies knockout studies and facilitates clear genotype-phenotype correlations, making it a preferred platform for CRISPR-based functional genomics. The CML context further supports the study of kinase-driven malignancy and targeted therapy evaluation.
Cyclin T1 is the regulatory subunit of P-TEFb, the essential transcription elongation factor that phosphorylates RNA polymerase II CTD at Ser2 and negative elongation factors DSIF and NELF to release paused polymerases. P-TEFb activity is modulated by the 7SK snRNP (HEXIM1/LARP7) inhibitory complex and activated by BRD4, HIV-1 Tat, and SEC components like AFF1 and ELL. Key upstream regulators including NF-??B and MYC promote P-TEFb release from 7SK, while Tat directly engages Cyclin T1 to recruit P-TEFb to the viral TAR element, dramatically enhancing HIV-1 transcription.
In the HAP1 CML model, CCNT1 knockout enables precise dissection of Cyclin T1??s role in both basal and Tat-dependent transcriptional elongation, as well as its contribution to leukemic cell proliferation. The near-haploid background enhances the sensitivity of CRISPR screens designed to identify synthetic lethal interactions or resistance mechanisms to CDK9 inhibitors. This system is particularly valuable for validating drug targets that disrupt P-TEFb function in oncogenic contexts.
These cells support a range of experimental approaches, including ChIP-seq to examine RNA polymerase II distribution, RNA-seq for global elongation profiling, and CDK9 kinase activity assays. HIV-1 Tat transactivation reporters can assess viral transcription dependency, while co-immunoprecipitation can probe P-TEFb complex assembly. Proliferation assays and CRISPR screens enable functional dissection of CCNT1-dependent pathways. For ordering or technical inquiries, please contact Ascent Research.
