Eukaryotic Transcription

by Georgina Cornwall, PhD

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    00:00 So now we need to look at little bit at eukaryotes and how things are different.

    00:07 Now, I mentioned earlier that there was only one RNA polymerase.

    00:09 I did lie a little bit.

    00:12 There are three that we know about now in eukaryotes.

    00:16 One of them is a polymerase.

    00:17 One, which is involved in making ribosomal RNAs.

    00:20 We don’t need to worry about those here.

    00:22 The other one is a polymerase III that is involved in making tRNA.

    00:27 And I introduced you to those in the last lecture.

    00:31 And finally, the one that we really care about is the eukaryotic RNA polymerase that’s involved in making messenger RNA in eukaryotes, is called RNA polymerase II.

    00:42 It is also involved in making some of the nuclear RNAs, but primarily, we are looking at it for the purposes if transcription in eukaryotic cells.

    00:52 So let’s see about some changes that we might see in transcription in eukaryotic cells.

    00:59 Naturally, it’s going to be a little bit more complex.

    01:04 And once again, we don’t necessarily know as much about it as we know about it in prokaryotic cells.

    01:11 We do know that we begin with the binding of a transcription factor to the promoter regions.

    01:19 So these transcription factors are going to help our RNA polymerase II bind to the promoter region and begin transcription.

    01:31 Each of them, we do have names for.

    01:35 I’m going to spare you the suffering of learning which ones arrive when and how.

    01:41 But either way, a bunch if transcription factors help everything assemble properly on the eukaryotic DNA strand.

    01:48 So these other transcription factors aid in getting the whole thing going.

    01:53 The point here though is these are all points at which we could regulate gene expression.

    02:01 We need all of these transcription factors to get going.

    02:04 If something’s absent, we’re not going to have transcription or maybe we’ll have it happen more slowly.

    02:10 But once all the transcription factors are assembled, then we know that RNA polymerase II can join the game and initiate transcription.

    02:21 So we form an initiation complex with the RNA polymerase and the transcription factors and we’re good to go.

    02:26 Now, one additional note, we are now learning that in addition to all the transcription factors, there are some elongation factors.

    02:36 And polymerase II will often very close to the initiation site or the transcription start site, will very often pause and it’s only with these elongation factors, other proteins, that come into play this transcription game, that we can push the polymerase further down the strand and get it going with the process of transcription.

    03:00 Otherwise, it will just hang out there and pause.

    03:04 So more potential for regulation of gene expression in eukaryotes because of all of the extra players that are also proteins that are also coded on DNA and need to be transcribed and translated in order to get the whole thing going.

    03:18 You’ll recall there are many mechanisms of cell communication and all of those come into play here.

    03:26 So it really could get quite complicated.

    About the Lecture

    The lecture Eukaryotic Transcription by Georgina Cornwall, PhD is from the course Gene Expression.

    Included Quiz Questions

    1. In prokaryotes, translation of the mRNA begins before transcription is complete. In eukaryotes, transcription and modification of the mRNA is completed before translation begins.
    2. In prokaryotes, genes are transcribed directly into polypeptides. In eukaryotes, genes are transcribed into RNA which is used to assemble polypeptides.
    3. In prokaryotes, translation occurs before genes are transcribed into mRNA. In eukaryotes, genes are transcribed into mRNA which is then translated into polypeptides.
    4. In prokaryotes, introns are removed before genes are transcribed into mRNA. In eukaryotes, introns are removed after genes are transcribed into mRNA.
    1. ...binding of a transcription factor to the TATA box, followed by recruitment of additional transcription factors and recruitment of RNA polymerase II.
    2. ...binding of a transcription factor to the transcription bubble, followed by recruitment of additional transcription factors and recruitment of RNA polymerase III.
    3. ...binding of RNA polymerase II to the TATA box, followed by recruitment of transcription factors.
    4. ...binding of a polymerase subunit to promoter elements at -35 and -10, followed by recruitment of the core polymerase.

    Author of lecture Eukaryotic Transcription

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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