Final answer:
RNA polymerase I in eukaryotes transcribes rRNA, RNA polymerase II transcribes mRNA, and RNA polymerase III is responsible for tRNA and 5S rRNA. Each polymerase binds to specific promoter sequences, with transcription factors playing key roles in the initiation of transcription.
Step-by-step explanation:
In eukaryotic cells, gene regulation involves the action of three distinct RNA polymerases, each responsible for transcribing different types of RNA. RNA polymerase I is responsible for transcribing ribosomal RNA (rRNA), specifically 18S, 5.8S, and 28S rRNAs. RNA polymerase II transcribes messenger RNA (mRNA), which encodes the blueprint for protein synthesis. Finally, RNA polymerase III synthesizes transfer RNA (tRNA) and 5S rRNA, which are essential for protein synthesis. The initiation of transcription requires the binding of transcription factors to specific promoter sequences, where the mRNA is synthesized in the 5' to 3' direction. While RNA polymerase II continues transcribing past the gene template and requires further processing of pre-mRNA, RNA polymerases I and III have different mechanisms for terminating transcription.