Cyclin-dependent kinase 7 (CDK7) is a pivotal enzyme that plays a crucial role in the regulation of the cell cycle. Its function is primarily exerted through the phosphorylation of other CDKs—namely CDK1, CDK2, CDK4, and CDK6—which are essential for their activation and subsequent progression of the cell cycle. Specifically, CDK7 activity during the G1 phase is necessary for the activation of CDK2, which in turn is crucial for the transition to the S phase. Conversely, the inhibition of CDK7 can delay this transition. Similarly, the inhibition of CDK7 during the S/G2 phase of the cell cycle can prevent the activation of CDK1, thereby blocking the entry into mitosis.

In addition to its role in cell cycle control, CDK7 is also instrumental in the regulation of transcription. It phosphorylates the RNA polymerase II (POLII) enzyme, which is a key step that allows POLII to be released from the pre-initiation complex (PIC) and commence the transcription of genes. Consequently, inhibiting CDK7 can have a significant impact on the transcriptome of cells, altering the expression of numerous genes. This dual functionality makes CDK7 a central player in both the control of cell proliferation and the regulation of gene expression.