How does RNA Polymerase work?

RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during transcription. While your uploaded file 01_Introduction.pdf references RNA polymerase only indirectly (e.g., in diagrams of the central dogma), here’s a detailed explanation that aligns with standard molecular neuroscience content and builds the bridge toward topics you will encounter later in the course.

🧬 How RNA Polymerase Works (in Eukaryotes)

1. Function

RNA polymerase (specifically RNA polymerase II in eukaryotic cells) catalyzes the transcription of DNA into precursor messenger RNA (pre-mRNA). This RNA is later processed into mature mRNA used for protein synthesis.

2. Transcription Cycle

A. Initiation

RNA Pol II cannot bind DNA directly; it is recruited to promoters (e.g., TATA boxes) by general transcription factors (GTFs).
Key steps:
1. TFIID, containing TATA-binding protein (TBP), binds the TATA box.
2. Other GTFs (TFIIB, TFIIF, TFIIE, TFIIH) assemble into a pre-initiation complex (PIC).
3. TFIIH unwinds DNA using helicase activity and phosphorylates the C-terminal domain (CTD) of RNA Pol II.
4. Phosphorylation of the CTD releases Pol II from the promoter into productive elongation.

B. Elongation

RNA Pol II reads the template strand of DNA in the 3′→5′ direction, synthesizing RNA in the 5′→3′ direction.
It unwinds DNA ahead of the active site and re-anneals it behind.
It incorporates ribonucleotides (ATP, UTP, CTP, GTP) complementary to the DNA template.

C. Termination

Transcription ends when Pol II passes specific termination signals, often after a polyadenylation signal (AAUAAA) is transcribed.
Termination mechanisms are complex and involve cleavage of the transcript and release of the polymerase.

3. Structural and Biochemical Features

RNA Pol II is a multi-subunit complex (~12 subunits in humans).
It includes:
- A DNA-binding cleft
- An active site with Mg²⁺ ions that catalyze phosphodiester bond formation
- A C-terminal domain (CTD) of the RPB1 subunit, whose phosphorylation state controls the transition between transcription phases and RNA processing

4. Regulation

Controlled by:
- Chromatin accessibility (e.g., via histone acetylation)
- Promoter and enhancer activity
- Transcription factors (e.g., CREB in neurons)
- Mediator complex, which bridges enhancers and Pol II

5. Relevance to Neuroscience

Neuronal gene expression is activity-dependent. For example:
- Synaptic activity leads to Ca²⁺ influx, activating transcription factors like CREB.
- These factors recruit co-activators and RNA Pol II, inducing transcription of immediate early genes (e.g., c-fos, Arc).

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Created: 10-06-25 19:39

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How does RNA Polymerase work?