RNA Interference

Hi in this video we're gonna be talking about RNA interference. Okay so RNA interference is a way to regulate transcripts. So the cell creates a lot of transcripts but not all of them. The cell wants to produce into proteins. So there's a few different ways that it can stop it and one of them is through RNA interference. Okay so RNA interference is called that because it interferes with the transcript and because it is a type of post transcription Elrod regulation occurring through RNA. So other than just where there's really no D. N. A. Involved here, it's all RNA that's being processed in a certain way and then binding to transcripts to stop their production into proteins and to stop anything from happening with them. Okay now there's two there's a lot of types of RNA interference. The two main ones, I mean the overwhelming majority of RNA interference is performed by what is called micro RNA S. Or M. I. R. N. A. S. So micro or S. I. R. N. A. S. And that S. I. Stands for short interfering but no one says short interfering but people sometimes do say MICRO RNA. So usually you hear micro RNA and then S. I. R. N. A. S. Is usually how you say these. Now these are different and they have to go through different processing in order for them to be able to stop the translation of a transcript. So micro RNA you can tell them apart because they're single stranded while S. I. R. N. A. S. R. Double stranded. So that's a big difference. You want to note the other main differences that MICRO RNA. S target a lot of different transcripts. So they're not just specific for one. When they're created they can stop transcription of multiple different RNA is right. They can stop transcription of tons of them. S. I. R. N. A. S. Are specific. They are used to stop the creation of one um or stop the translation of one transcript. Okay so they're gonna block one transcript while micro RNA are gonna block a ton of them. So because MICRO RNA are single stranded and S. RNA are double stranded, they've got to be processed differently. So MICRO RNA is how they're produced is they're often found in non coding regions of genes. So they're found in the N. Tron. They're found upstream of the start code on or downstream of the start coat on and things that wouldn't normally be found in a gene or be processed right? Usually these parts are cut out and destroyed. So the micro RNA is there produced from a gene that's transcribed but then something has to come in and cut out the entrance for entrance and then inside that N tron there's a micro RNA. Now we have this long piece of RNA, not all of it is the mic the micro RNA but there's an enzyme called dicer and that dicer enzyme jumps on to say that in tron or that piece of non coding RNA and it jumps on it and it says there's a micro RNA here. And what it does is it chops off all the excess nucleotides and it gets down to around 22 nucleotides. Um and um and it cuts off all that extra part that's called a pre micro RNA. And it cuts it down to about 22 nucleotides can be a little more, little less. Why that squiggly is there? But generally 22 nuclei nucleotides. And that's the micro RNA. Before it was cut it's called the pre micro RNA. And then after it's cut called the micro RNA. So now we have our 22 nucleotide micro RNA. It's going to come and interact with another enzyme that enzymes called risk. And when it will bind to risk then it goes on to bind to the transcript, it's going to stop, Right? So its purpose is to destroy various different transcripts. So when you have the micro RNA A. Plus the risk enzymes, they'll actually bind onto those transcripts and destroy them and mark them for destruction. Okay. And they do that because the micro RNA has nucleotides and these nucleotides can be complementary to the RNA transcripts it's going to destroy. So when it's in risk risk is going to help it find these complementary transcripts, it's going to bind to it and that's going to mark it for destruction. Now S I RNA are different because they actually start out as double stranded meaning that at some point the RNA has folded upon itself and formed something like a hairpin loop. Right? We can see these sometimes because RNA forms secondary structures, right? It forms three D. Structures. So an S. I. R. N. A. Often starts out looking like this. So these same enzymes are used, we have die. So this would be a pre. S. I. R. N. A. Then we get dicer to come in, dicer comes in and it cleaves this out. So it says nope. Don't need you don't need you. This is my S. My S. I. RNA is here. So it cleans the pre S. I. RNA forms the S. I. R. N. A. Then risk comes in and this is different from micro RNA. Because this is where we turn that double stranded S. I. R. N. A. Into a single stranded. So the risk comes in says nope, you're double stranded. You need to be single stranded, digests one of those strands. And now it adds similar to micro RNA. Is and that it's targeted to a specific transcript through complementary base pairing and then um that is destroyed. So here we're going to look at it S. I. RNA. We know it's an S. RNA. Because it's double stranded S. RNA. Right here. So dicer comes onto this piece of double stranded RNA says there's a micro RNA here. So I'm gonna chop off chop all these other parts off and allowing for this S. RNA to sit in here. Risk comes in. This purple enzyme says, whoa, you're an S. I. R. N. A. We have a job to do but you're still double stranded. And so it digests that red strand, it sort of degrades it. And now we have what's called the guide strand or that strand that's left and then risk and the strand that's left. The S. I. R. N. A. Is going to find an RNA with a complementary sequence bind to it and mark it for destruction. Okay, so once this is bound, this transcript is going to be destroyed, it is not going to be translated. Okay, so that is RNA interference with that. Let's move on.

siRNAs target a variety of different RNA transcripts for degradation.

• A. True
• B. False

Which of the following enzymes are responsible for cleaving and processing miRNAs and siRNAs?

• A. DICER
• B. RISC
• C. Guide RNA enzymes
• D. RNA polymerase II

MiRNAs and siRNAs target degradation of RNA transcripts by binding to what?

• A. RNA polymerase II
• B. The gene promoter
• C. A gene transcript
• D. The spliceosome