Cyclin-Dependent Kinase 7 Controls mRNA Synthesis by Affecting Stability of Preinitiation Complexes, Leading to Altered Gene Expression, Cell Cycle Progression, and Survival of Tumor Cells

Abstract

Cyclin-dependent kinase 7 (CDK7) activates cell cycle CDKs and is a member of the general transcription factor TFIIH. Although there is substantial evidence for an active role of CDK7 in mRNA synthesis and associated processes, the degree of its influence on global and gene-specific transcription in mammalian species is unclear. In the current study, we utilize two novel inhibitors with high specificity for CDK7 to demonstrate a restricted but robust impact of CDK7 on gene transcription in vivo and in in vitro-reconstituted reactions. We distinguish between relative low- and high-dose responses and relate them to distinct molecular mechanisms and altered physiological responses. Low inhibitor doses cause rapid clearance of paused RNA polymerase II (RNAPII) molecules and sufficed to cause genome-wide alterations in gene expression, delays in cell cycle progression at both the G₁/S and G₂/M checkpoints, and diminished survival of human tumor cells. Higher doses and prolonged inhibition led to strong reductions in RNAPII carboxyl-terminal domain (CTD) phosphorylation, eventual activation of the p53 program, and increased cell death. Together, our data reason for a quantitative contribution of CDK7 to mRNA synthesis, which is critical for cellular homeostasis.

ACKNOWLEDGMENTS

This work was supported by the German Ministry for Research and Technology (BMBF; grant number 0313860D), followed by an internal grant of the IZKF of Faculty of Medicine of the Westfalian Wilhelms University (WWU) Muenster to M.M. and the Max Planck Foundation, Munich, Germany, to the Lead Discovery Center. We are grateful to the IZKF of the Faculty of Medicine of the WWU Muenster for support. We also thank the Excellency initiative Cells in Motion and the Cell Dynamics and Disease graduate school for supporting M.M. and T.W.R.K., respectively.

We further thank the members of the M.M. laboratory for support during the experimental phase and for helpful discussions.