Answer
Role of Rho (ρ) Factor in Transcription Termination
The rho (ρ) factor plays a vital role in the termination of transcription in prokaryotic organisms. It is a protein that functions as an RNA-dependent ATPase and helicase. The rho factor is involved in a specific mechanism known as rho-dependent termination.
During transcription, once the RNA polymerase synthesizes a region of RNA that contains a rho recognition site (also known as a rut site), the rho factor binds to this site on the nascent RNA transcript. Using energy derived from ATP hydrolysis, rho travels along the RNA in the 5′ to 3′ direction, moving toward the RNA polymerase.
When the RNA polymerase pauses at a termination site downstream, the rho factor catches up. At this point, rho utilizes its helicase activity to disrupt the RNA-DNA hybrid within the transcription bubble. This disruption causes the release of the RNA transcript and dissociation of the RNA polymerase from the DNA template, effectively terminating transcription.
This mechanism ensures that transcription ends precisely at the correct point, preventing unnecessary extension of the RNA and ensuring accurate gene expression. The rho factor is therefore essential for maintaining the integrity and regulation of gene transcription in prokaryotes.