RNA Polymerase III, also known as Pol III, transcribes tRNA and the 5S subunit of ribosomal RNA. It is composed of 17 subunits and weighs around 700 kDa. The genes transcribed by Pol III are directly in association with cell cycle and cell growth, therefore this enzyme needs to be active at all times and in every environment. Pol III does not require a heavy assemblage of TFs like Pol II.