Which type of RNA is NOT synthesized by eukaryotic RNA polymerase III?

Eukaryotic RNA polymerase III is responsible for synthesizing several types of small RNAs, including transfer RNA (tRNA), small rRNA, and microRNA (miRNA). However, messenger RNA (mRNA) is not synthesized by RNA polymerase III; instead, it is produced by RNA polymerase II.

RNA polymerase III primarily synthesizes the following types of RNA:

• tRNA, which is essential for translation as it brings amino acids to the ribosome.
• Small rRNA, notably the 5S rRNA component of the ribosome.
• miRNA, which plays a crucial role in regulating gene expression.

mRNA is a key product that carries genetic information from DNA to the ribosome for protein synthesis and is therefore synthesized by RNA polymerase II. This distinction is fundamental in understanding the functions of RNA polymerases in the eukaryotic transcription machinery.