Which RNA polymerase is responsible for transcribing rRNA?

RNA polymerase I is primarily responsible for transcribing ribosomal RNA (rRNA), which is a key component of ribosomes. Ribosomes play a critical role in protein synthesis, as they serve as the site where mRNA is translated into polypeptides. The specific type of rRNA transcribed by RNA polymerase I includes 28S, 18S, and 5.8S rRNA, all of which are essential for forming the structural and functional backbone of ribosomes.

To add more context, RNA polymerase II is mainly involved in transcribing messenger RNA (mRNA) and certain small nuclear RNAs (snRNAs). RNA polymerase III transcribes other small RNAs, including transfer RNA (tRNA) and 5S rRNA. RNA polymerase IV, which is found in plants, is involved in the production of small interfering RNAs (siRNAs) that are tied to RNA silencing mechanisms.

This specialization of RNA polymerases underscores the complexity and regulation of gene expression within the cell, where different types of RNA polymerases are tasked with the transcription of different classes of RNA molecules.