The CCNT1 Knockout NCI-H1299 Polyclonal Cells consist of a CRISPR/Cas9-edited polyclonal cell population with targeted disruption of the CCNT1 gene encoding cyclin T1, the regulatory subunit of positive transcription elongation factor b (P-TEFb). This heterogeneous pool avoids clonal selection bias and ensures reproducible knockout effects across experiments. The cells serve as a robust loss-of-function tool for dissecting P-TEFb-dependent transcriptional regulation.
The NCI-H1299 cell line, derived from a lymph node metastasis of a lung adenocarcinoma patient, is a widely used non-small cell lung cancer (NSCLC) model. These cells harbor a TP53 deletion and exhibit high metastatic potential, making them suitable for studying tumor progression and therapeutic response. The CCNT1 knockout in this aggressive background provides a relevant system to examine transcriptional elongation in cancer.
Cyclin T1 partners with CDK9 to form the P-TEFb complex, which phosphorylates RNA polymerase II CTD at Ser2 to drive transcriptional elongation. It is essential for HIV-1 Tat-mediated transactivation, recruiting P-TEFb to viral promoters. Upstream signals from NF-??B, MYC, and PI3K/AKT regulate CCNT1 activity, leading to expression of downstream targets like c-MYC, BCL2, and MCL1. CCNT1 also interacts with 7SK snRNP (via HEXIM1) for sequestration and with BRD4 for chromatin recruitment, linking epigenetic cues to elongation.
In NCI-H1299 cells, CCNT1 knockout disrupts P-TEFb function, impairing expression of MYC- and NF-??B-driven genes critical for proliferation and survival. This exposes vulnerabilities in transcriptional addiction, enabling studies of synthetic lethality and drug sensitivity. The loss of cyclin T1 also abrogates HIV-1 replication, making the cells valuable for antiviral research. The polyclonal nature ensures phenotypes are not artifacts of clonal expansion.
Applications include western blot analysis of CCNT1 and phospho-Ser2 RNA Pol II, RT-qPCR for c-MYC and BCL2, RNA-seq, and ChIP-qPCR to profile transcriptional changes. In HIV studies, p24 ELISA quantifies Tat-dependent transcription. Cellular assays such as MTT, annexin V staining, and flow cytometry assess proliferation and apoptosis. Combinatorial inhibitor studies with CDK9 or BRD4 inhibitors further elucidate P-TEFb pathway dynamics. For product inquiries, contact Ascent Research.
