What type of RNA does RNA polymerase I transcribe?

RNA polymerase I is responsible for transcribing ribosomal RNA (rRNA), which is a crucial component of the ribosome, the cellular machinery involved in protein synthesis. This type of RNA forms the structural and functional core of ribosomes, combined with proteins to facilitate the translation of messenger RNA (mRNA) into polypeptides.

The specialization of RNA polymerase I in synthesizing rRNA aligns with its primary function in the nucleolus, where ribosomal RNA is produced and subsequently processed and assembled with ribosomal proteins to form ribosomes. Understanding this relationship is key to grasping how gene expression is tightly regulated and how different types of RNA are synthesized for specific cellular roles.

In contrast to RNA polymerase I, other RNA polymerases specialize in different types of RNA. RNA polymerase II, for example, synthesizes mRNA, while RNA polymerase III transcribes tRNA and small nuclear RNA (snRNA). Each polymerase has distinct functions that are critical for the overall process of gene expression within the cell.