Transcription in Prokaryotes

Transcription includes initiation, elongation, and termination.

The bacterial core RNA polymerase binds a sigma factor, forming a holoenzyme for initiation.

This sigma factor interacts with promoter regions, like the -35 and -10 sequences, positioning the RNA polymerase near the transcription start site.

After binding, the holoenzyme unwinds the DNA at the -10 site, exposing the template strand.

The sigma factor dissociates after adding a few ribonucleotides, and the core RNA polymerase continues elongating the RNA until it encounters a terminator sequence.

Bacterial transcription termination occurs through intrinsic signals in the RNA transcript, which form stem-loop structures, or through proteins like Rho factors, which dissociate RNA polymerase and RNA.

In archaeal promotors, the TATA-binding protein binds to the TATA box, while transcription factor B recognizes the B recognition element sequence. These factors recruit the RNA polymerase to the initiation site.

Termination in archaea occurs via intrinsic signals in the RNA transcript, like the stem-loop structures, and is independent of protein factors.