Describe the difference between rho-dependent and rho- independent termination of transcription. describe the mechanisms of both termination types
The Correct Answer and Explanation is:
Rho-dependent and rho-independent termination are two distinct mechanisms that stop transcription in bacteria, specifically during the process where RNA is synthesized from DNA. Both methods ensure that the RNA molecule detaches from the DNA template once the gene is fully transcribed, but the mechanisms involved are different.
Rho-Dependent Termination:
In rho-dependent termination, the process involves a protein called Rho. This protein is a helicase, which moves along the RNA strand towards the RNA polymerase that is synthesizing the RNA. The Rho protein binds to a specific sequence on the newly synthesized RNA, called the rut site (Rho utilization site). Once bound, Rho uses its ATPase activity to move along the RNA strand, following the polymerase. When Rho catches up to the RNA polymerase, it causes the polymerase to dissociate from the DNA template, thus terminating transcription. The primary feature of this type of termination is the dependence on the Rho protein.
Rho-Independent Termination:
Rho-independent termination, also known as intrinsic termination, does not require any external protein like Rho. Instead, it relies on specific sequences in the RNA itself. The RNA sequence forms a hairpin loop structure, followed by a series of uracil (U) bases. The formation of the hairpin loop creates a physical barrier that causes the RNA polymerase to pause. This pause is further stabilized by the U-rich region, which weakly binds to the DNA template. The weak A-U base pairing leads to the release of the RNA transcript from the DNA, effectively terminating transcription. The key features of this process are the hairpin loop and the U-rich sequence.
Key Differences:
- Proteins Involved: Rho-dependent termination requires the Rho protein, while rho-independent termination does not rely on any protein.
- Mechanism: Rho-dependent termination uses the Rho helicase to physically remove RNA polymerase from the DNA, while rho-independent termination relies on RNA sequence features like the hairpin loop and U-rich region to terminate transcription.
