Transcription !

Transcription copies a DNA gene into an RNA molecule; in eukaryotes three RNA polymerases do it with the help of transcription factors.

Updated 2026-11-01

Key facts

RNA polymerase reads the template strand 3'→5' and makes RNA 5'→3'; it needs no primer and does not proofread.
Pol I: 28S, 18S and 5.8S rRNA (nucleolus). Pol II: mRNA, most snRNAs and microRNAs. Pol III: tRNA, 5S rRNA.
Pol II promoter: TATA box (about −25 to −30) and elements such as CAAT and GC boxes; enhancers can lie far away.
TFIID (with the TATA-binding protein, TBP) binds first; TFIIH opens the DNA and phosphorylates Pol II's C-terminal domain (CTD).
Rifampicin inhibits bacterial RNA polymerase; α-amanitin inhibits human Pol II.

Initiation: the general factors (TFIID, TFIIA, TFIIB, TFIIF, TFIIE, TFIIH) and Pol II form the preinitiation complex on the promoter.
Phosphorylation of CTD serine 5 releases the polymerase from the promoter and recruits the capping enzyme; phosphorylated serine 2 recruits splicing and polyadenylation factors.
Elongation: the transcription bubble moves along with about 17 bp open; the RNA–DNA hybrid is about 8–9 bp long.
Termination in eukaryotes: after the AAUAAA signal the RNA is cut and the polymerase falls off. In bacteria: a GC-rich hairpin followed by U's, or the rho factor.
Activators bind enhancers and, through Mediator, help assemble the machinery; repressors and silencers do the opposite.
Bacteria have a single RNA polymerase (α₂ββ'ω) that finds the promoter with the σ factor (−10 Pribnow and −35 boxes).

Rifampicin, a backbone of tuberculosis treatment, blocks the β subunit of bacterial RNA polymerase; rpoB mutations cause resistance.
Amanita mushroom poisoning shuts down Pol II in the liver and causes hepatic necrosis.
Actinomycin D intercalates into DNA and stops transcription; it is used in some childhood tumours.

Think of the answer, then tap the question to see it.

Which eukaryotic RNA polymerase makes mRNA, and what is its classic toxin?

RNA polymerase II; it is inhibited by α-amanitin from Amanita mushrooms.

What does TFIIH do at transcription initiation?

It opens the double helix with its helicase activity and phosphorylates Pol II's CTD so it leaves the promoter.

How does RNA polymerase differ from DNA polymerase regarding primers?

RNA polymerase starts without a primer; DNA polymerase needs a free 3'-OH.

Which antituberculosis drug inhibits bacterial transcription?

Rifampicin, which binds the β subunit (rpoB) of bacterial RNA polymerase.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Gene expression (Transcription) (Reactome, 2026); RNA Polymerase II Transcription (Reactome, 2026); How do genes direct the production of proteins?: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.