rna Pol Ii is the focus of eukaryotic transcription, because it is the most studied polymerase and is also responsible for transcribing most genes-indeed essentially all protein-encoding genes a RNA Pol I transcribe the large ribosomal RNa precursor gene RNA Pol II transcribe tRNA gene some small nuclear RNA genes and the 5s rRNA genes11 ◼ RNA Pol II is the focus of eukaryotic transcription, because it is the most studied polymerase, and is also responsible for transcribing most genes-indeed, essentially all protein-encoding genes ◼ RNA Pol I transcribe the large ribosomal RNA precursor gene ◼ RNA Pol II transcribe tRNA gene, some small nuclear RNA genes and the 5S rRNA genes