Which eukaryotic RNA polymerase is inhibited by alpha-amanitin at very low concentrations and is responsible for synthesis of messenger RNA precursors?

• A RNA polymerase I
• B RNA polymerase III
• C RNA polymerase II ✓
• D Mitochondrial RNA polymerase

Explanation

RNA polymerase II transcribes protein-coding genes into hnRNA (pre-mRNA) and is exquisitely sensitive to alpha-amanitin, the toxin of Amanita phalloides, which binds the enzyme and halts mRNA synthesis, producing fatal hepatotoxicity. RNA polymerase I synthesizes 45S rRNA precursor and requires very high amanitin concentrations for inhibition, while RNA polymerase III transcribes tRNA and 5S rRNA and shows intermediate sensitivity. Mitochondrial RNA polymerase is not an amanitin target.

Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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