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The Levels of Eukaryotic Gene Expression

by Georgina Cornwall, PhD
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    00:01 Welcome back. Let us move on to take a look at regulation of gene expression in eukaryotic cells. By the end of this lecture, you should be able to describe the multiple levels of regulation that are possible in eukaryotes as well as diagram components of the transcription complex and discuss how DNA packing can impact gene expression as well as explain some other mechanisms of regulation. Let us begin by looking at the potential levels of regulation in eukaryotes because eukaryotic cells have a nucleus. We have separation of transcription and translation. We also have the production of messenger RNA so on and so forth. There is a lot more possibility at many levels. First of all, we have how DNA is packed in the nucleus. Is it available? So the chromatin can be modified in a number of ways that we'll discuss shortly. We have our DNA and the process of transcription naturally can have lots of different regulatory mechanisms. We will spend quite a bit of time there and then we take our RNA and that primary transcript needs to be modified to remove axons and put on a five prime cap and a poly A tail. RNA processing provides us with RNA. All of that stuff can be regulated. Once we have that primary or that immature messenger RNA it can be transported into the cytosol where it will have a number of different options. It could be degraded or it could be translated and we get a polypeptide and if everything is in place there, then the polypeptide will then go on to be modified after translation and folded and change a little bit to finally form an active protein and then that protein could be modified by being broken down and we have some degraded protein. Many many levels at which we could regulate the expression of genes. Interruptions can happen anywhere. It is amazing that genes ever get expressed, isn't it? With always possible points. Naturally we will only be discussing about once we know. We know quite a bit about the regulation of transcription and so we will really be beginning there. Let us take a look at the eukaryotic promoter regions. Of course, there are going to be many places that we can regulate during the transcriptional process and so the pieces in the puzzle for eukaryotic transcription are even more tricky to understand than it would be in prokaryotic. I am going to make it simple as I can for you. Let us look at the promoter region and then the gene sequence.

    02:51 We have a promoter region similar to what we saw in prokaryotic cells and there are some seriously conserved regions in that promoter space. The TATA box is something we are interested in because that is where the RNA polymerase will bind. But there is other conserved regions just as they did with prokaryotes will allow the polymerase and all the other machinery to recognise which direction we need to go along the genes, which strand is the template and which strand is coding. Once we start transcription, there is going to be some blank space, which will code for the five prime untranslated regions and at the end some blank space for the three prime untranslated regions on RNA. Again those were to help the RNA associate with its ribosome get it to the right place. Not totally sure of the mechanisms there, but we do know if we clip them off, it doesn't really work so well.

    03:54 Let us take a look at transcriptional control. There are lots of players. When I introduced


    About the Lecture

    The lecture The Levels of Eukaryotic Gene Expression by Georgina Cornwall, PhD is from the course Gene Regulation.


    Included Quiz Questions

    1. The UTRs play critical roles in ribosome binding, translation initiation, translation termination and post-transcriptional gene expressions.
    2. The UTRs help in the initiation of transcription process by guiding the RNA pol to bind at TATA box.
    3. The UTRs of mRNA help in the charging of tRNA with their respective amino acids.
    4. The UTRs of tRNA help in the exclusion of the exons to create an entirely functional mature mRNA molecule.
    5. The UTRs prevent the premature termination of replication and transcriptional processes.
    1. Proximal promoter ----- A binding site for RNA polymerase
    2. 5’ UTR ----- Ribosomal binding and initiation of translation
    3. 3’ UTR ----- Post-transcriptional gene expression regulation
    4. Core promoter ----- Minimum portion of promoter needed for initiation of transcription
    5. TATAAA sequence ----- Bind to TATA-binding proteins to assist RNA pol transcriptional complex

    Author of lecture The Levels of Eukaryotic Gene Expression

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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