15. Central Dogma & Gene Regulation
Eukaryotic RNA Processing and Splicing
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In this video we're going to talk about RNA processing. And so RNA processing only occurs in eukaryotic organisms, not in prokaryotic organisms. And so eukaryotic RNA processing involves 2 events that are gonna alter both ends of the premature mRNA, or the pre mRNA. And so the first event is going to be the addition of a 5 prime cap, which is really just a modified guanine nucleotide that's going to be added specifically to the 5 prime end of the pre mRNA. And then the second event that's going to alter the end of the pre mRNA is the addition of a poly a tail. And the poly a tail is really just a sequence of a bunch of adenine nucleotides that are gonna be added specifically to the 3 prime end of the pre mRNA. And so both of these alterations are going to modify the ends of the pre mRNA. And so if we take a look at our image down below, what you'll notice is over here on the left hand side, what we've got is our premature mRNA, our pre mRNA immediately after transcription. And so this pre mRNA, we know that in eukaryotic cells is going to go undergo RNA processing, which involves modifying the end of the pre mRNA. So you can see the ends are being modified. The first modification involves the addition of a 5 prime cap, which is added to the 5 prime end of the RNA molecule. And, again, the 5 prime cap is really just a modified guanine nucleotide. Now on the 3 prime end of the RNA molecule, it is also going to be modified, but with a poly a tail. And the poly a tail is just a stretch of a bunch of adenine nucleotides that are added to the 3 prime end of the RNA molecule. Now you might be wondering, why is it that the 5 prime cap and the poly a tail need to be added to the RNA. And so it turns out that the 5 prime cap and the poly a tail actually share several important functions, including the following functions that we are listing down below. The 5 prime cap and poly a tail are both important for facilitating exports of the mRNA from the nucleus where it's first transcribed in eukaryotic organisms to the cytoplasm where the RNA molecule needs to be in order for translation to take place, which, again, we'll talk more about translation later in our course. But the 5 prime cap and poly A tail are really important to export the mRNA from the nucleus to the cytoplasm. Now the 5 prime cap and poly A tail are also really important to protect the mRNA from degradation by enzymes. And so the addition of the 5 prime cap and the poly a tail helps to, again, protect the mRNA from degradation by enzymes that might otherwise degrade the RNA. Now lastly, the 5 prime cap and poly a tail are both important for helping ribosomes attach to the mRNA for translation to take place. And so we'll be able to talk again more about translation later in our course. But, these ribosomes are cellular structures that are important for translation. And so these ribosomes need to be able to attach to the mRNA, and the 5 prime cap and poly A tail play a role in that attachment. And so, this here is going to conclude our brief introduction to RNA processing. And so in our next video, we'll be able to talk about RNA splicing. So I'll see you all in that video.
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