Riboswitches - Online Tutor, Practice Problems & Exam Prep

Riboswitches are mRNA sequences located in the 5' untranslated region that bind small molecules, regulating their own gene expression. They consist of two main domains: an aptamer, which binds the ligand, and an expression platform that forms a secondary structure, often a terminator structure, to control transcription and translation. This mechanism allows riboswitches to interfere with both processes in prokaryotic cells, affecting gene regulation effectively. Understanding riboswitches enhances knowledge of gene expression control and RNA functionality in cellular processes.

Riboswitches

Hi. In this video, we're going to be talking about riboswitches. So I kind of think riboswitches are kind of the coolest things ever, but I don't know. Maybe after this video you'll agree with me. So what are riboswitches? Riboswitches are mRNA sequences found in the 5' prime region, which stands for the region that obviously is not translated into protein, but it's still present in the mRNA. And so it's the sequence in the 5' prime untranslated region, and it binds small molecules, just molecules in general, and this controls gene expression of the mRNA itself. And so, riboswitches control the expression of themselves. It controls the expression of that mRNA sequence where the riboswitch exists. And so there are 2 main domains in a riboswitch. There is an aptamer, and this is the RNA sequence. Remember, when we were dealing with RNA, is an RNA sequence that binds to the small molecule, and then you have an expression platform. So after that is bound, a secondary structure forms and this regulates gene expression, and the secondary structure forms in this expression platform. So a common structure that will form is called the terminator structure. Now, all of these I feel like everything in this chapter is called the same thing, but it means different depending on which operon or what you're talking about, but for a riboswitch, the terminator structure, is a structure formed by binding the small ligand, and it terminates the translation. So riboswitches actually have the ability to interfere with transcription. It has the ability to interfere with splicing and translation. Now, it can interfere with transcription because remember, we're talking about prokaryotic cells, in these topics, and prokaryotic cells transcription and translation occur in the same compartment. And so riboswitches, even though they're happening on mRNA, can actually in the 5' prime regional region, it can affect transcription and translation. So when it stops transcription, ribos, so transcription termination, so the termination of transcription is controlled through that terminator structure, which I talked about before, and translation termination is controlled through a termination structure, so the same structure, but this one actually will block a ribosome binding site. So it can affect both transcription and translation depending on when and where all these structures are found. So this is what they look like. I think they have a really cool structure. One of the questions I hope that you're asking right now is you're saying, okay, well this is RNA, What are all these letters standing for? Why are there w's, k's, d's, y's, etcetera? Well, you'll notice here, any of the red ones, I believe, red and then some of these orange ones, these are actually nucleotides. And all of these stand for RNA nucleotides, but they stand for different things. Now I don't know the key off the top of my head, but we could say, well, W would stand for A or U, K would stand for T, G, or U. And all of these are different codes, and they stand for different combinations of what nucleotide could be there. But all of these little circles represent some type of nucleotide, even if it's not saying which nucleotide it represents and instead is in a code. So hopefully you asked that question. Notice here that this is 5' prime and 3' prime, so it goes down like this, creates these structures, goes all the way back around, and ends up here. So we're going that way, right, all the way around. So riboswitches are so cool. Hopefully, you think so too, but this is definitely a type of prokaryotic gene regulation, which can stop transcription or translation. So, with that, let's now move on.

Riboswitches are made up of what type of molecule?

• A. RNA
• B. DNA
• C. Protein

Which of the following processes can riboswitches NOT interfere with?

• A. Enhancers
• B. Transcription
• C. Splicing
• D. Translation