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.