In bacteria, what is the role of rho factor in transcription termination?

• A. It dissociates the transcription complex at rut sites
• B. It forms hairpin structures in RNA
• C. It polyadenylates RNA
• D. It synthesizes mRNA

Answer: (A)

Rho-dependent termination uses the rho factor as a helicase that binds to rut sites on the nascent RNA and uses ATP to translocate along the transcript toward the RNA polymerase. When it catches up to a paused RNA polymerase, rho destabilizes the RNA–DNA–protein transcription complex, causing the RNA transcript to be released and the polymerase to dissociate from the DNA. This specific action at rut sites is how rho terminates transcription in many bacteria. Intrinsic termination, by contrast, relies on a hairpin structure in the RNA and a downstream U-rich region, not on rho. Polyadenylation in bacteria is more about RNA turnover than termination, and RNA polymerase, not rho, synthesizes mRNA.