Which RNA polymerase transcribes tRNA and 5S rRNA?

• A. RNA polymerase II
• B. RNA polymerase IV
• C. RNA polymerase I
• D. RNA polymerase III

Answer: (D)

Small noncoding RNA genes, including tRNA and 5S rRNA, are transcribed by RNA polymerase III. This polymerase specializes in short, noncoding transcripts and uses specific transcription factors to start correctly at these genes. In comparison, RNA polymerase I makes the bulk of the ribosomal RNA precursors (the large rRNAs), and RNA polymerase II transcribes mRNA and many snRNAs. RNA polymerase IV is a plant-specific enzyme involved in siRNA pathways. Therefore, the RNA polymerase that transcribes tRNA and 5S rRNA is RNA polymerase III.