16. Regulation of Expression
Eukaryotic Post-Transcriptional Regulation
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In this video, we're going to talk about the first level of post transcriptional regulation in eukaryotes, and that is alternative RNA splicing. And so recall that way back in our previous lesson videos, we already covered alternative RNA splicing. And so if you don't remember anything about alternative RNA splicing, then make sure to go back and watch those older videos before you continue here. And so recall that eukaryotes require post transcriptional modifications like RNA splicing, which can alter gene expression. And so alternative splicing is really when different mRNA molecules are produced from the same premature RNA molecule or the same pre mRNA. And so another way to be able to phrase alternative splicing is, because there are different mRNA molecules produced, that's going to lead to different proteins being made from the same gene. And so different mRNA molecules will lead to different proteins being made Now recall that the spliceosome, Now recall that the spliceosome is the complex RNA protein, complex, that is going to remove introns from the pre mRNA and splice together the exons. And so if we take a look at our image down below over here again, we have our miniature map and you can see that we're focusing on RNA processing, and this is going to be a form of post transcriptional modifications the spl the splicing here that we're referring to. And so, up at the top here, what we have is the DNA, the specific gene of interest. And within the gene, the red regions here represent exons that are gonna be spliced together, and the blue regions represent introns introns that are going to be removed. And so, notice that, when the gene is first transcribed through transcription, it's a pre mRNA molecule or a pre mRNA transcript that is formed. And the pre mRNA molecule is, not going to be, the fully mature mRNA. It must undergo, splicing. And so over here, what we are zooming into is the spliceosome formation, which is going to be an assembly of, complex of RNA and protein that will come together to remove the introns, remove the blue regions, and splice together the red regions, the exons. And so that's what we're referring to here as RNA splicing. And alternative RNA splicing is when, RNA splicing can occur in multiple different ways. There are alternative pathways for RNA splicing to occur. And so here in this image, we're focusing on just 2 different alternative pathways for RNA splicing to occur. The first RNA pathway RNA splicing pathway is over here on the left hand side, which is showing you exons 123 all being expressed. And this is going to be the fully mature this is the mature mRNA that's ready for translation. And so this is one possibility for the RNA to get spliced, and that would create this particular circular protein product upon translation. But the alternate RNA splicing pathway over here, notice, has a different mature mRNA transcript where exon 3, notice, is not available over here. It's not present. And so exon 3 acted as an intron, in this alternative RNA splicing pathway. And so exon 3 was removed as an intron. And so only exons 1, 2, and 4 are available over here. And that creates a shorter polypeptide chain and that ultimately leads to a different protein. And so by filtering and controlling alternative RNA splicing, a specific gene product, can be redirected to create a new gene product. And so this is a way of regulating gene, expression. And so this is a post transcriptional method because, the alternative RNA splicing is occurring after transcription has occurred. And so this here concludes our, brief review and introduction here of alternative RNA splicing. And we'll be able to get some practice applying this as we move forward and talk about the other forms of post transcriptional regulation. So I'll see you all in our next video.
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