Question

RECALL List the Pol II general transcription factors.

Short answer

TFIID, TFIIB, TFIIF, TFIIE, TFIIH.

Step-by-step solution

Understanding General Transcription Factors

General transcription factors (GTFs) are essential for initiating transcription by RNA polymerase II (Pol II). They help to assemble the transcription pre-initiation complex and position Pol II at the start site of transcription.

Identify Pol II General Transcription Factors

The general transcription factors associated with Pol II are: TFIID, TFIIB, TFIIF, TFIIE, TFIIH.

Review the Functions of Each Factor

Briefly review the role of each factor:TFIID - Recognizes and binds to the TATA box in the core promoter.TFIIB - Binds to DNA and stabilizes TFIID binding.TFIIF - Escorts Pol II to the transcription start site.TFIIE - Recruits and regulates TFIIH.TFIIH - Has helicase activity to unwind DNA and kinase activity to phosphorylate Pol II.

Key concepts

Transcription Initiation

Transcription initiation is the process by which the information in DNA is copied into mRNA. This is a crucial step in gene expression and is tightly regulated to ensure that genes are expressed at the right time and in the right amount. During initiation, RNA polymerase II (Pol II) and general transcription factors assemble at the promoter region of a gene. This assembly forms the transcription pre-initiation complex, positioning Pol II for the start of RNA synthesis.
The key steps in transcription initiation include:

• Binding of general transcription factors to the core promoter.
• Recruitment of Pol II to the transcription start site.
• Unwinding of DNA to expose the template strand.
• Initiation of RNA synthesis by Pol II.

General Transcription Factors

General transcription factors (GTFs) are proteins that are essential for the transcription of all Pol II genes. They are involved in the formation of the transcription pre-initiation complex, which is necessary for the proper positioning of Pol II at the start site of transcription.
The main GTFs involved with Pol II are:

• TFIID
• TFIIB
• TFIIF
• TFIIE
• TFIIH

These factors work together to ensure that Pol II can bind to the promoter region and initiate the synthesis of RNA.
Each GTF plays a specific role in the transcription initiation process, which will be discussed in more detail in the following sections.

RNA Polymerase II

RNA polymerase II (Pol II) is the enzyme responsible for transcribing most protein-coding genes in eukaryotes. It synthesizes messenger RNA (mRNA) from a DNA template during transcription.
Pol II's main functions include:

• Binding to the promoter region with the help of GTFs.
• Unwinding the DNA template to allow for mRNA synthesis.
• Catalyzing the formation of RNA by adding nucleotides complementary to the DNA template.

Pol II's activity is regulated by various mechanisms, including the phosphorylation of its C-terminal domain (CTD) by kinase activity.
This regulation ensures proper timing and efficiency of transcription in response to cellular signals.

TFIID

TFIID is a multi-subunit complex that is crucial for the initiation of transcription by Pol II. It recognizes and binds to the TATA box, a DNA sequence found in the core promoter of many genes.
The primary roles of TFIID include:

• Binding to the TATA box and other promoter elements.
• Recruiting other GTFs and Pol II to form the pre-initiation complex.
• Facilitating the open complex formation by allowing DNA to unwind.

Subunits of TFIID, such as TBP (TATA-binding protein), play crucial roles in promoter recognition and binding.

TFIIB

TFIIB is essential for stabilizing the binding of TFIID to the core promoter and for the recruitment of Pol II to the transcription start site. It acts as a bridge between TFIID and Pol II, ensuring proper positioning of the transcription machinery.
Key functions of TFIIB include:

• Binding to the BRE (B recognition element) sequence in the promoter.
• Stabilizing TFIID binding to the promoter.
• Assisting in the recruitment of Pol II to the pre-initiation complex.

TFIIB's interaction with both DNA and Pol II is crucial for the correct assembly of the transcription initiation complex.

TFIIF

TFIIF plays a critical role in escorting Pol II to the transcription start site and stabilizing its interaction with the DNA template. It works closely with other GTFs to ensure efficient transcription initiation.
Functions of TFIIF include:

• Binding to Pol II and assisting its recruitment to the promoter.
• Stabilizing the unwound DNA template.
• Reducing the likelihood of non-specific binding of Pol II to DNA.

TFIIF's association with Pol II helps maintain the stability of the transcription initiation complex and promotes the synthesis of the RNA transcript.

TFIIE

TFIIE is crucial for recruiting and regulating TFIIH, a key factor with helicase and kinase activities. It facilitates the transition from the transcription initiation phase to the elongation phase.
Roles of TFIIE include:

• Binding to the transcription pre-initiation complex.
• Recruiting TFIIH to the complex.
• Regulating the activities of TFIIH.

TFIIE's interaction with both the pre-initiation complex and TFIIH is vital for the successful initiation of transcription and the subsequent elongation phase.

TFIIH

TFIIH is a multi-functional factor with critical roles in transcription initiation and DNA repair. It has helicase activity to unwind DNA and kinase activity to phosphorylate Pol II. These activities are essential for allowing Pol II to proceed with transcription.
Key functions of TFIIH include:

• Unwinding the DNA template to expose the transcription start site.
• Phosphorylating the C-terminal domain (CTD) of Pol II.
• Facilitating the transition from transcription initiation to elongation.

TFIIH's dual helicase and kinase activities are crucial for the dynamic processes of DNA unwinding and Pol II regulation during transcription.