Other Levels of Eukaryotic Gene Regulation

by Georgina Cornwall, PhD

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    00:01 Let us say we have our messenger RNA on its way to translation. We are getting there. It has not been edited. Nothing happens to it. First of all did it get out of the nucleus? Depending on the number of the nuclear pores present at that time, mRNA may be blocked from exiting the nucleus and it could also be blocked from binding with the ribosome. We could have lots of enzymes out in the cytosol there to jump up that poly A tail take off the hat and break down RNA so that it is not even available to the ribosomes. And then again just like with prokaryotes we have this issue of translation and we have to have a lot of things for successful translation, all the tRNAs all the different tRNA synthesizers that put the aminoacids on the tRNAs, the pieces of the ribosomes, lots and lots of proteins involved there, of course, all of them need to be present for translation to happen. If they are not present, translation itself could be stalled. So again, many proteins, much complexity in the control of gene expression in eukaryotes. Finally, when we think about proteins that we did actually get made, the ribosome did assemble, all of the pieces were there, we get a protein that is functional right? Not necessarily. As we had in the introductory series in this lecture, we could have a protein that is degraded. All of that happens and now we don’t need the protein and so we are going to chop it.

    01:42 A fairly recent work has come about noticing that a molecule called ubiquitin is added to proteins that are destined to be degraded. So the ubiquitin is on that protein and that protein can enter the protein break down area called the proteasome and the proteasome will break it down only if it has ubiquitin labelled on it, kind of sucks it in there, chops it up, breaks it down, releases the ubiquitin and that ubiquitin can then be recycled to tag the other proteins. A key player in there is ubiquitin ligase, just like ligase in DNA replication, ligase is a glue, so ubiquitin ligase is going to ligate or stick ubiquitin onto those proteins and ubiquitin on those proteins will add enough ubiquitin then it will get picked up by the proteasome and broken down. So investment of ATP is critical in breaking these down. It doesn't make sense to make a protein that needs to be broken down immediately of course, but this is one of the ways that proteins are tagged for disposal. Anyway, lots of different levels for regulation of gene expression in eukaryotes and I can guarantee you that as time goes on what we know is going to grow and thus your understanding of it will become more and more complex of our system to understand. It is definitely a field to stay aware of and open to learning more about.

    03:20 But at this point you should be able to describe multiple levels of regulation in eukaryotes, think about each of the levels we could regulate as well as diagram the components of these transcription complexes. And discuss DNA packing and its impact on gene expression as well as explain other mechanisms of regulation along the way of production of a final active protein. Thank you so much for listening and I look forward to seeing you in the next lecture.

    About the Lecture

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

    Included Quiz Questions

    1. …ubiquitin.
    2. …poly-A tail.
    3. …poly-A cap.
    4. ...miRNA.
    5. …siRNA.

    Author of lecture Other Levels of Eukaryotic Gene Regulation

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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    Great lecture!
    By Simbongile M. on 07. September 2017 for Other Levels of Eukaryotic Gene Regulation

    great lecture! I still feel the need to fill in the gaps but it has given me an overview of gene regulation