P-TEFb

RNA polymerase II elongation control

P-TEFb

P-TEFb, short for Positive Transcription Elongation Factor b, is a crucial protein complex involved in the regulation of transcription elongation in eukaryotic cells. It plays a significant role in the control of gene expression by facilitating the transition from transcription initiation to elongation.

Structure

P-TEFb is composed of two main subunits: Cyclin-dependent kinase 9 (CDK9) and Cyclin T. CDK9 serves as the catalytic subunit, while Cyclin T acts as a regulatory subunit that targets CDK9 to specific substrates. The complex is essential for the phosphorylation of RNA polymerase II, which is necessary for efficient transcription elongation.

Function

P-TEFb functions by phosphorylating the C-terminal domain of RNA polymerase II, leading to the release of paused polymerase and allowing for productive elongation of the transcript. This process is critical for the expression of many genes, including those involved in cell growth, differentiation, and development.

Regulation

The activity of P-TEFb is tightly regulated in cells to ensure proper control of gene expression. Various factors, such as cellular signaling pathways and transcription factors, can influence the activity of P-TEFb by modulating its association with other proteins or by regulating its kinase activity.

Role in Disease

Dysregulation of P-TEFb has been implicated in various diseases, including cancer and viral infections. In cancer, aberrant activation of P-TEFb can lead to uncontrolled cell proliferation and tumor growth. Additionally, some viruses hijack P-TEFb to promote their own replication within host cells.

See also

• Transcription (biology)
• RNA polymerase II
• Cyclin-dependent kinase 9