Question

At which step of bacterial transcription does the sigma (σ) factor dissociate from the RNA polymerase?

Options

• At the –10 region (Pribnow Box)

• After transcription has terminated and the RNA is released

• During promoter recognition, before DNA binding

• Once transcription begins, after initiation

Answer 1

The sigma (σ) factor dissociates from the RNA polymerase core enzyme once transcription begins, after the initiation phase is complete. This means the σ factor is only required for promoter recognition and DNA melting at the initiation site. After the polymerase enters the elongation phase and moves along the template, the σ factor is released and can be recycled to facilitate initiation of other genes.