2) mRNA Protection in the Cytoplasm

Jason Amores Sumpter
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in this video, we're going to talk about the second level of post transcription regulation, which is mRNA protection in the cytoplasm. And so mRNA transcripts must be transported to the cytoplasm of the cell in order for the mRNA transcript to be translated by ribosomes and create a protein product. But the problem is, is that the cytoplasm actually has many RNA degrading enzymes. And so the M RNA transcripts. When they go out to the cytoplasm, they are at risk of being degraded by these RNA degrading enzymes. Now these are in a degrading enzymes are there to help destroy foreign viral RNA molecules so they are going to act as a defense mechanism against viral RNA molecules. Now, in order for the mRNA transcripts to be protected, the M RNA needs to be processed so that it has a five prime cap added as well as a poly a tail added as well. And so the five prime cap and the poly a tail, which is added to the three prime end of the molecule. Um, that is going to protect the M RNA from degradation by enzymes. And so this degradation feature and, uh, non and protection feature degradation and protection is a way of regulating gene expression. And so let's take a look at our image down below to get a better understanding of this. And so notice the example here says that M. R N A. Is protected from degradation by cytoplasm enzymes with a five prime cap and a poly a tail. And so RNA processing, which is the addition of the five prime Captain Poly. A tail occurs within the nucleus, but of course the RNA needs to be transported to the outside into the cytoplasm of the cell. And so it needs to be transported outside the nucleus into the cytoplasm of the cell. And so that's what you see here. Here we have the nucleus. This entire box here is representing a cell, and within the cell we have the nucleus of the cells right here and within the nucleus. You can see we have our mature M RNA here, and it must be transported out of the nucleus. Now if the mRNA is not protected, if it does not have a five prime cap in a poly a tail, then it's going to be an unprotected mRNA. And that's going to lead to degradation. So the unprotected M R N A. Is degraded over here and notice that it's being chopped up into a bunch of tiny little pieces. And then, in that case, the final gene product, the protein is not going to be created. And so this is a way of turning off. The gene is through, uh, making sure that the RNA is unprotected. That will turn off the gene. Now, of course, if the R N A is properly protected with the five prime cap and the poly a tail, then we have a protected M RNA that will not be degraded. And this protected mRNA that's not degraded. It can therefore be translated into a protein. And, of course, when it's translated into a protein, the final gene product is being made. And so this is a way of turning on the gene and so you can see the off and the on. This is a way of regulating gene expression to turn on or turn off genes. And so this year concludes our introduction to this second level of post transcription allele regulation, and we'll be able to get some practice applying these concepts as we move forward, as well as talk about the third and final level of post transcription regulation, So I'll see you all in that video.