While miRNA response elements (MREs) may be located anywhere within an mRNA, they are most often found outside the coding region in the 5' or 3' UTR. Explain why this is likely the case given that miRNAs often target more than one mRNA.

Video transcript

Hi, everybody. Let's take a look at this practice problem together. Micro RNA, S M I R N A s are a class of non coding RNA is that play important role in the regulation of gene expression. One single M I R N A usually targets many genes and one gene might be regulated by multiple M I R N A s. The reason for multiple targets is recall that M I R N A plays a role in the regulation of gene expression how by binding their target M R N A s. So the reason for multiple targets is what is it A M I RNA binding sites included, not only three prime untranslated regions, but also five prime untranslated regions and coding sequences. So that's a long one and we'll come back to that be short base pairs within M I R N A three prime untranslated region duplex C, both A and B or dean, none of the above. Now, let's discuss a further and I'd like to review a depiction of M RNA with the regions mentioned in a. Here, we have an M RNA strand, We have the five prime end a five prime untranslated region, A coding sequence, a three prime untranslated region. And then the three prime end, typically, when M I RNA binds, it creates a duplex and binds to the three prime untranslated region. However, it can also bind the coding sequence as well as the five prime untranslated region. So here alone on this single M RNA strand, there's 123 different possibility of the M RNA targeting and binding this M RNA strand. Therefore, a is a true statement and one of the reasons for multiple targets. Now let's talk about B short based pairs with an M I R N A three prime untranslated region duplex. So that's referring to when the M I RNA binds here with the three prime untranslated region. Now, it's important to note that when it binds, it does not have to have perfect binding to the target. M RNA is the binding, however, does have to be perfect within a region called a seed region. What is the seed region? Well, it is on the M I R N A, It's closer to the five prime end And it's usually 6-8 nucleotides long. So when M I RNA binds its target M R N A, that seed region has to have perfect binding. Other sections may not have perfect pairing or perfect binding. So given this short number of bases within the seed region and considering the vast amount of bases in the human genome, that means M I R N A s can easily bind hundreds of targets. So B is also true. Therefore, the correct answers options. See both A N B. Alright, everyone. Thanks for hanging in with me. I know this video is a bit of a longer one. I hope you found it helpful though and I'll see you next time for the next practice problem.