RNA Polymerase III

In eukaryote cells, RNA polymerase III (also called Pol III) transcribes DNA to synthesize ribosomal 5S rRNA, tRNA and other small RNAs. This enzyme complex has a more limited role than the Pol III in prokaryote cells.

The genes transcribed by RNA Pol III fall in the category of "housekeeping" genes whose expression is required in all cell types and most environmental conditions. Therefore the regulation of Pol III transcription is primarily tied to the regulation of cell growth and the cell cycle, thus requiring fewer regulatory proteins than RNA polymerase II.

In the process of transcription (by any polymerase) there are three main stages:

1. Initiation; requiring construction of the RNA polymerase complex on the gene's promoter.
2. Elongation; the writing of the RNA transcript.
3. Termination; the finishing of RNA writing and disassembly of the RNA polymerase complex.