Transcription Termination in Prokaryotes: Videos & Practice Problems

In prokaryotes, transcription termination occurs via two mechanisms: factor-dependent and rho-dependent termination. Factor-dependent termination involves the formation of a stem-loop structure in mRNA, causing RNA polymerase to dissociate from DNA. In contrast, rho-dependent termination relies on the rho protein binding to a specific site on mRNA, leading to the release of RNA polymerase. Both processes ensure the completion of messenger RNA synthesis, highlighting the intricate regulation of gene expression in prokaryotic organisms.

Transcription Termination in Prokaryotes

This video, we're going to begin our lesson on transcription termination, specifically in prokaryotes. In prokaryotes, the termination of transcription can occur in one of two different ways as numbered below. The first way that transcription termination can occur in prokaryotes is through factor-dependent termination. The second way that transcription can occur in prokaryotes is through rho-dependent termination. Factor-dependent termination involves the mRNA, or the messenger RNA, forming what's known as a stem-loop structure. This stem-loop structure occurs when the mRNA starts to hydrogen bond with itself to create a loop within its structure, and we'll be able to see that down below. When the mRNA forms this stem-loop structure, it causes the termination of transcription. The change in the mRNA structure causes the RNA polymerase to dissociate from the DNA, leading to the termination of transcription.

If we look at our image on the left-hand side, it focuses on factor-dependent termination. In factor-dependent termination, as shown in the image, the RNA polymerase, depicted in pink, starts to elongate the mRNA. The DNA is shown in blue in the background. In factor-dependent termination, the mRNA forms a stem-loop structure, highlighted in a blue background. The formation of the stem-loop structure ultimately causes the RNA polymerase to dissociate. The RNA polymerase dissociates from the DNA, releases the mRNA, and now termination is complete, and the mRNA has been created. This is the first way that transcription termination can occur in prokaryotes.

The second way is through rho-dependent termination. As its name implies, rho-dependent termination depends on a rho protein. The terminator protein rho, which can be symbolized by the Greek letter rho, binds to the mRNA and causes the termination of transcription. The rho protein binds to a rho site on the mRNA, and this interaction ultimately causes the RNA polymerase to dissociate from the DNA, leading to the termination of transcription.

Note on the image on the right-hand side focusing on rho-dependent termination. This is where the Greek symbol for rho is shown. In this termination process, the rho protein, depicted in yellow and circled in blue, binds to a specific site on the mRNA called the rho site. At that point, the rho protein begins a process that ultimately leads to the dissociation of the RNA polymerase. Notice that the RNA polymerase is dissociated, the rho protein dissociates, and once again the mRNA is complete, signaling that the termination of transcription is complete.

This concludes our brief lesson on the two possible ways that prokaryotes can terminate transcription through factor-dependent termination or rho-dependent termination. We'll be able to get some practice applying these concepts and learn more as we move forward. So I'll see you all in our next video.

The rho protein functions in:

• A. Protein secretion.
• B. Termination of transcription.
• C. Initiation of translation.
• D. Termination of translation.
• E. Release of ribosome from the mRNA.

Answer: (B)

Which of the below statements is false?

• A. Factor-dependent and rho-dependent termination are both methods for stopping DNA replication.
• B. Factor-dependent termination involves a hairpin or stem-loop structure.
• C. Rho-dependent termination involves the rhoprotein.
• D. All of the above are true.

Answer: (A)

Here’s what students ask on this topic:

What are the two main mechanisms of transcription termination in prokaryotes?

In prokaryotes, transcription termination occurs via two main mechanisms: factor-dependent termination and rho-dependent termination. Factor-dependent termination involves the formation of a stem-loop structure in the mRNA, which causes the RNA polymerase to dissociate from the DNA, thereby terminating transcription. On the other hand, rho-dependent termination relies on the rho protein binding to a specific site on the mRNA, known as the rho site. This binding leads to the release of RNA polymerase from the DNA, completing the transcription process. Both mechanisms ensure the proper synthesis and regulation of messenger RNA in prokaryotic cells.

How does factor-dependent termination work in prokaryotes?

Factor-dependent termination in prokaryotes involves the formation of a stem-loop structure in the mRNA. This structure is created when the mRNA hydrogen bonds with itself, forming a loop. The formation of this stem-loop structure causes a change in the mRNA's conformation, which leads to the dissociation of RNA polymerase from the DNA. As a result, transcription is terminated, and the newly synthesized mRNA is released. This mechanism ensures that the transcription process is properly concluded, allowing the mRNA to be used for protein synthesis.

What role does the rho protein play in rho-dependent termination?

In rho-dependent termination, the rho protein plays a crucial role by binding to a specific site on the mRNA known as the rho site. Once bound, the rho protein moves along the mRNA towards the RNA polymerase. This interaction causes the RNA polymerase to dissociate from the DNA, thereby terminating transcription. The rho protein's ability to bind and move along the mRNA is essential for the proper regulation and completion of the transcription process in prokaryotic cells.

What is the significance of the stem-loop structure in factor-dependent termination?

The stem-loop structure in factor-dependent termination is significant because it induces the termination of transcription. This structure forms when the mRNA hydrogen bonds with itself, creating a loop. The formation of the stem-loop causes a conformational change in the mRNA, which leads to the dissociation of RNA polymerase from the DNA. This dissociation effectively ends the transcription process, ensuring that the mRNA is properly synthesized and ready for translation. The stem-loop structure is thus a critical element in the regulation of gene expression in prokaryotes.

How does rho-dependent termination differ from factor-dependent termination?

Rho-dependent termination differs from factor-dependent termination in its reliance on the rho protein. In rho-dependent termination, the rho protein binds to a specific site on the mRNA, known as the rho site, and moves along the mRNA towards the RNA polymerase. This interaction causes the RNA polymerase to dissociate from the DNA, terminating transcription. In contrast, factor-dependent termination involves the formation of a stem-loop structure in the mRNA, which causes the RNA polymerase to dissociate from the DNA. Both mechanisms ensure the proper termination of transcription but utilize different processes to achieve this goal.