Transcription factor II F

Transcription factor II F (TFIIF) is a complex of proteins that plays a pivotal role in the process of transcription in eukaryotic cells. It is one of several general transcription factors (GTFs) required for the initiation of transcription by RNA polymerase II (Pol II). TFIIF is involved in the stabilization of the RNA polymerase II binding to DNA and the initiation of gene transcription. It also plays a role in the elongation phase of transcription and helps in promoter clearance.

Function

TFIIF has multiple functions in the transcription process. Initially, it assists in the formation of the pre-initiation complex (PIC) by stabilizing the interaction between RNA polymerase II and the other general transcription factors. This stabilization is crucial for the assembly of a competent transcription initiation complex. Once the PIC is formed, TFIIF helps in the start of the transcription process by reducing the affinity of RNA polymerase II for nonspecific DNA sequences, thereby increasing its processivity. Furthermore, TFIIF is involved in promoter clearance, which is the transition from transcription initiation to elongation. This role is essential for the RNA polymerase II to move beyond the promoter and start synthesizing RNA.

Structure

TFIIF is a heterodimer composed of two subunits: RAP30 and RAP74, which are named based on their molecular weights in kiloDaltons. These subunits interact with each other and with RNA polymerase II, facilitating the formation of a stable transcription initiation complex. The structure of TFIIF allows it to interact with other transcription factors and with the RNA polymerase II enzyme, positioning it as a critical mediator in the transcription initiation process.

Regulation

The activity of TFIIF, like other transcription factors, is regulated at multiple levels. Post-translational modifications (PTMs) such as phosphorylation can affect its function and interaction with RNA polymerase II and other transcription factors. The regulation of TFIIF activity ensures that transcription initiation occurs in a controlled manner, coordinating with the cell's needs and environmental signals.

Clinical Significance

Alterations in the function or expression of TFIIF can have significant implications for cellular function and can contribute to the development of diseases, including cancer. For example, dysregulation of transcription initiation, including the function of TFIIF, can lead to aberrant gene expression patterns that promote oncogenesis. Understanding the role of TFIIF in transcription and its regulation offers potential therapeutic targets for diseases associated with transcriptional dysregulation.

See Also

• Transcription (genetics)
• RNA polymerase II
• General transcription factor
• Gene expression