In bacteria, the transcription of all the three types of RNA (mRNA, tRNA, rRNA) is catalysed by single DNA-dependent enzyme, called the RNA polymerase. The RNA polymerase has co-factors β, β', α, α' and ω along with σ (sigma) factor that catalyse the process. During initiation, σ factor recognises the start signal and promoter region on DNA, and the (Sigma) with RNA polymerase binds to the promoter.
