Panoply™ Human CDK19 Knockdown Stable Cell Line

The Mediator complex regulates RNA polymerase II transcription across the entire genome. A common factor regulating Mediator function is the four-subunit kinase module, which contains either cyclin-dependent kinase 8 (CDK8) or CDK19. CDK8 is associated with specific signaling pathways and tumorigenesis, while the cellular functions of its homolog, CDK19, are largely unknown. Researchers found that osteosarcoma cells (SJSA) naturally lack CDK8 protein. Although SJSA cells can tolerate stable CDK19 knockdown, cell proliferation is inhibited. Notably, re-expression of wild-type or kinase-inactive CDK19 restores cell proliferation. Comparative RNA sequencing analysis showed that in CDK19 knockdown cells, the expression of mitosis-related genes was decreased, while the expression of genes related to cholesterol metabolism and the p553 pathway was increased. Treatment of SJSA cells with 5-fluorouracil (which induces metabolic and genotoxic stress and activates p53) further confirmed the involvement of CDK19 in the expression of p53 target genes. To better investigate the p53 response, researchers treated SJSA cells (shCDK19 and shCTRL) with the p53 activator nutlin-3. Notably, CDK19 is crucial for SJSA cells to recover their proliferative state after nutlin-3 treatment, and this effect is independent of kinase activity. These results indicate that CDK19 is a regulator of the p53 stress response and suggest that CDK19 plays a role in cellular resistance to nutlin-3.

RNA sequencing data showed that cholesterol and lipid homeostasis-related gene expression was upregulated in CDK19 knockdown SJSA cells compared to control SJSA cells. To further investigate this, researchers measured total cholesterol levels in control and CDK19 knockdown cells, but no difference was observed (Figure 1A). Furthermore, researchers assessed whether changes in cellular cholesterol levels would affect the recovery of SJSA cells after treatment with nutlin-3. To increase cholesterol biosynthesis intermediates, they treated control and CDK19 knockdown SJSA cells with mevalonate (MVA) and mevalonate phosphate (MVAP). As shown in Figure 1B, MVA plus MVAP treatment did not significantly affect the recovery of SJSA cells after nutlin-3 treatment. As previously observed, CDK19 knockdown cells failed to recover to a proliferative state (blue curve, Figure 1B), while control cells began to proliferate approximately 48 hours after treatment (green curve, Figure 1B).

Figure 1. Analysis of cholesterol in control cells versus CDK19 knockdown cells. (Audetat K A, et al., 2017)