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A Kinase-Independent Role for Cyclin-Dependent Kinase 19 in p53 Response
K Audrey Audetat1,2, Matthew D Galbraith3, Aaron T Odell2,4
1Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, USA.
Abstract:
The human Mediator complex regulates RNA polymerase II transcription genome-wide. A general factor that regulates Mediator function is the four-subunit kinase module, which contains either cyclin-dependent kinase 8 (CDK8) or CDK19. Whereas CDK8 is linked to specific signaling cascades and oncogenesis, the cellular roles of its paralog, CDK19, are poorly studied. We discovered that osteosarcoma cells (SJSA) are naturally depleted of CDK8 protein. Whereas stable CDK19 knockdown was tolerated in SJSA cells, proliferation was reduced. Notably, proliferation defects were rescued upon the reexpression of wild-type or kinase-dead CDK19. Comparative RNA sequencing analyses showed reduced expression of mitotic genes and activation of genes associated with cholesterol metabolism and the p53 pathway in CDK19 knockdown cells. SJSA cells treated with 5-fluorouracil, which induces metabolic and genotoxic stress and activates p53, further implicated CDK19 in p53 target gene expression. To better probe the p53 response, SJSA cells (shCDK19 versus shCTRL) were treated with the p53 activator nutlin-3. Remarkably, CDK19 was required for SJSA cells to return to a proliferative state after nutlin-3 treatment, and this effect was kinase independent. These results implicate CDK19 as a regulator of p53 stress responses and suggest a role for CDK19 in cellular resistance to nutlin-3.
Insights
Cyclin-dependent kinase 19 (CDK19) regulates cell proliferation and p53 stress responses. CDK19 is crucial for osteosarcoma cells to recover proliferation after p53 activation, independent of its kinase activity.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The Mediator complex is a key regulator of RNA polymerase II transcription.
- The Mediator kinase module, containing CDK8 or CDK19, modulates Mediator function.
- While CDK8 is linked to oncogenesis, CDK19's cellular roles are largely unknown.
Purpose of the Study:
- To investigate the cellular functions of CDK19, particularly in osteosarcoma cells.
- To determine CDK19's role in cell proliferation and stress response pathways.
Main Methods:
- Osteosarcoma cell line (SJSA) with natural CDK8 depletion.
- Stable CDK19 knockdown and reexpression experiments.
- Comparative RNA sequencing and p53 activation assays using nutlin-3 and 5-fluorouracil.
Main Results:
- CDK19 knockdown in SJSA cells reduced proliferation and altered gene expression, including downregulating mitotic genes and upregulating cholesterol metabolism and p53 pathway genes.
- CDK19 was essential for SJSA cells to regain proliferation after p53 activation by nutlin-3.
- This recovery of proliferation was independent of CDK19's kinase activity.
Conclusions:
- CDK19 plays a significant role in regulating cell proliferation and is a key component of the p53 stress response pathway.
- CDK19 is implicated in cellular resistance to nutlin-3 treatment, suggesting a broader role in stress adaptation.