Rho-dependent termination

Definition

Rho-dependent termination is a mechanism in prokaryotic transcription where the Rho protein facilitates the release of the newly synthesized RNA transcript from the RNA polymerase enzyme. This process occurs when the RNA transcript has a specific sequence that allows Rho to bind and utilize its helicase activity to unwind the RNA-DNA hybrid, leading to the dissociation of RNA polymerase from the DNA template and the termination of transcription.

5 Must Know Facts For Your Next Test

1. Rho-dependent termination is characterized by the presence of a specific sequence in the RNA called the Rho utilization site (rut site) that Rho binds to.
2. This termination mechanism requires energy, as Rho uses ATP hydrolysis to facilitate its helicase activity.
3. Unlike intrinsic termination, which relies on specific RNA sequences forming hairpin structures, rho-dependent termination requires the Rho protein's activity.
4. Rho-dependent termination occurs after RNA polymerase transcribes the rut site and can occur regardless of whether there are downstream hairpin structures.
5. The efficiency of rho-dependent termination can be influenced by factors such as the rate of RNA polymerase movement and interactions with other proteins.

Review Questions

• How does rho-dependent termination differ from intrinsic termination in prokaryotic transcription?
  • Rho-dependent termination and intrinsic termination are both mechanisms to stop transcription, but they operate differently. Intrinsic termination relies on specific sequences in the RNA that form stable hairpin structures, leading to the dissociation of RNA polymerase without any additional factors. In contrast, rho-dependent termination requires the Rho protein, which binds to a specific sequence in the RNA and utilizes its helicase activity to separate the RNA transcript from the DNA template, actively promoting transcription termination.
• Discuss the role of the Rho protein in facilitating rho-dependent termination and how it interacts with RNA polymerase.
  • The Rho protein is essential for rho-dependent termination as it binds to the Rho utilization site on the newly synthesized RNA transcript. Once bound, Rho uses its helicase activity, fueled by ATP hydrolysis, to unwind the RNA-DNA hybrid at the transcription bubble. This unwinding leads to the dislodging of RNA polymerase from the DNA template. By actively promoting this release, Rho ensures that transcription is efficiently terminated when necessary.
• Evaluate how external factors might influence rho-dependent termination efficiency during prokaryotic transcription.
  • The efficiency of rho-dependent termination can be significantly affected by various external factors, including the speed of RNA polymerase during transcription and interactions with other regulatory proteins. For instance, if RNA polymerase moves too quickly through a rut site, Rho may not have enough time to bind effectively and terminate transcription. Additionally, competing factors such as ribosomes translating mRNA can hinder Rho's access to RNA, potentially leading to read-through transcription. Thus, understanding these influences is vital for comprehending gene regulation in prokaryotes.

Related terms

Rho protein: A hexameric protein that plays a crucial role in rho-dependent termination by binding to the RNA transcript and promoting the release of RNA polymerase.

Transcription termination: The final step in transcription where RNA synthesis is halted, leading to the release of the RNA molecule from the DNA template.

RNA polymerase:

The enzyme responsible for synthesizing RNA from a DNA template during transcription in prokaryotes.