What is the role of CDK7?

Cyclin-dependent kinase 7 (CDK7) is a vital regulatory protein in cells that plays a significant role in regulating both the cell cycle and gene expression. It is a member of the cyclin-dependent kinase (CDK) family, which means it works together with other proteins called cyclins to control the timing of cell cycle events. CDK7 is also part of a complex known as CDK-activating kinase (CAK), which activates other CDKs, allowing the cell to progress through its various stages. Besides its important role in the cell cycle, CDK7 also helps control transcription, the process by which cells make RNA copies of genes. This makes CDK7 an essential player in both cell division and gene regulation, ensuring that the cell functions properly and responds to its environment.

Role of CDK7 in Cell Cycle Regulation

CDK7 plays an important role in the regulation of the cell cycle, helping cells transition from one phase to another. Its main function is to activate other CDKs, which are needed to move the cell forward through the different stages of the cycle.

1. Activation of Other CDKs

  • One of the key functions of CDK7 is to activate other cyclin-dependent kinases like CDK1, CDK2, CDK4 and CDK6. It achieves this by phosphorylating them, which means adding a phosphate group to them, a step that is necessary for their activation. These activated CDKs are responsible for controlling the transition between different phases of the cell cycle, such as from G1 to S phase (DNA replication) and from G2 to M phase (mitosis). Without CDK7's activation of these other CDKs, the cell would not be able to progress properly through the cycle, which could result in cell cycle arrest or genomic instability.

2. Ensuring Controlled Cell Cycle Progression

  • By activating the necessary CDKs, CDK7 ensures that the cell progresses through the cell cycle at the right time and in an orderly manner. This control is crucial because improper progression can lead to genetic mutations, cancer, or other cell dysfunctions. CDK7's activity ensures that the cell only moves on to the next stage of the cycle when it is ready, protecting the cell from potential damage.

Role of CDK7 in Transcription Regulation

Apart from its role in the cell cycle, CDK7 is also involved in transcription regulation. It is part of a larger complex called TFIIH (Transcription factor II H), which is necessary for RNA polymerase II to transcribe genes into messenger RNA (mRNA).

1. Phosphorylation of RNA Polymerase II

  • CDK7, as part of TFIIH, phosphorylates the C-terminal domain (CTD) of RNA polymerase II. This modification is critical for the transition from transcription initiation to elongation, allowing RNA polymerase II to continue the process of gene transcription. Without this phosphorylation, transcription would be stuck at the initial stage, preventing the cell from producing necessary proteins.

2. Regulation of Gene Expression

  • By regulating RNA polymerase II, CDK7 controls the expression of genes. This is important because gene expression is responsible for making proteins that are crucial for cell functions, such as growth, response to stress and repair. By ensuring proper transcription, CDK7 helps the cell respond to changes in its environment and maintain normal function.






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