RNA polymerase III

RNA polymerase III is a DNA dependant RNA polymerase that transcribes double stranded DNA to single stranded mRNA.
RNA polymerase III is the main RNA polymerase for prokaryotic cells.

The RNA polymerase, in the absence of sigma subunit, is called the core enzyme which inly contains the catalytic site.
Binding of the RNA pol III requires sigma factor 70 as the sigma subunit (σ) enables the RNA polymerase to recognise the promoter site. Sigma factor usually binds at -35- -10 base pairs. The sigma factor RNA polymerase complex moves along the DNA together for the first 10 base pairs then sigma dissociates leaving RNA polymerase to transcribe until the termination sequence.

Reference