Question

In Transcription, which among these Transcription factors have Helicase activity

• A. TFIID
• B. TFIIB
• C. TFIIE
• D. TFIIH

Hint:

Remember the H in TFII\textbf{H} stands for \textbf{H}elicase. It's the last factor to join the preinitiation complex and performs the crucial ATP-dependent unwinding and kinase activities that get transcription started.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
In eukaryotic transcription initiation by RNA Polymerase II, a series of general transcription factors (TFIIs) assemble at the promoter to form the preinitiation complex (PIC). One of these factors is responsible for unwinding the DNA helix at the transcription start site, which requires helicase activity.
Step 2: Detailed Explanation:
The general transcription factors assemble in a specific order:
TFIID (containing TBP, the TATA-binding protein) binds to the TATA box in the promoter.
TFIIA stabilizes the TFIID-DNA complex.
TFIIB binds and helps recruit RNA Polymerase II.
TFIIF binds to RNA Polymerase II and helps it associate with the promoter complex.
TFIIE then joins the complex and is crucial for recruiting and regulating the final factor, TFIIH.
TFIIH is a large, multi-subunit complex with multiple enzymatic activities. Critically, it possesses helicase activity (specifically, the XPB subunit) that uses ATP to unwind the DNA at the transcription start point, creating the "transcription bubble." TFIIH also has kinase activity that phosphorylates the C-terminal domain (CTD) of RNA Polymerase II, allowing it to escape the promoter and begin elongation.
Step 3: Final Answer:
Among the listed transcription factors, TFIIH is the one that contains the helicase activity necessary for unwinding the promoter DNA.