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: Introduction:
In eukaryotic transcription, RNA Polymerase II initiates transcription with the help of general transcription factors (TFIIs) that assemble at the promoter to form the preinitiation complex (PIC). A key factor unwinds the DNA helix at the transcription start site, using helicase activity.
Step 2: Factor Assembly:
General transcription factors assemble in this order:
TFIID (with TBP) binds to the TATA box.
TFIIA stabilizes the TFIID-DNA complex.
TFIIB binds and recruits RNA Polymerase II.
TFIIF binds RNA Polymerase II and helps it associate with the promoter.
TFIIE joins the complex, recruiting and regulating TFIIH.
TFIIH is a multi-subunit complex with enzymatic activities. It has helicase activity (XPB subunit) that unwinds DNA at the transcription start point, forming the "transcription bubble." TFIIH also phosphorylates the C-terminal domain (CTD) of RNA Polymerase II, enabling promoter escape and elongation.
Step 3: Conclusion:
TFIIH, among the transcription factors, contains the helicase activity to unwind the promoter DNA.