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16. Regulation of Expression

Eukaryotic Transcriptional Control

16. Regulation of Expression

Eukaryotic Transcriptional Control

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1

concept

Introduction to Transcription Factors

3m

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in this video, we're going to begin our lesson on eukaryotic transcription control. And so you carry. It can also regulate their gene expression by utilizing DNA binding proteins. And these DNA binding proteins will bind to regulatory regions in a gene to help control transcription. Now these DNA binding proteins are actually called transcription factors and so down below. Here we're introducing transcription factors and so recall from our previous lesson videos. That transcription initiation in eukaryotes requires a complex of transcription factors bound to a promoter sequence. And so transcription factors, as their name implies, are going to be factors that are important for transcription. And more specifically, they're going to be proteins, proteins that are going to bind to specific DNA sequences and regulate transcription, initiation and help promote transcription. And so really, there are two main types of transcription factors and eukaryotes. There are general transcription factors, and then there are specific transcription factors and so down below in our image, we're giving you some brief information on general and specific transcription factors. But as we move forward in our course, we're going to talk even more details about general and specific transcription factors, and so notice here in this image, what we're showing you are is a DNA molecule in the background, which has two strands. One that goes five prime 23 prime, uh, from left to right and the other strand goes five Prime prime from right to left and notice that within the DNA there's going to be a promoter region, which is highlighted here in green. And then there's going to be the coding sequence of the gene. And so the general transcription factors are going to be binding to the promoter region, and they are required for transcription of all genes, which is why they are called general transcription factors because they are in general, required for the transcription of all jeans. Now, specific transcription factors, on the other hand, do not necessarily bind directly to the promoter. They combined to other regulatory regions around a gene, and so these specific transcription factors are not required for all jeans. Instead, they are going to be required for the transcription of a specific gene of specific genes, and so some jeans require specific transcription factors. But all genes require general transcription factors, and so, once again, as we move forward in our course, we're going to continue to talk more details about general and specific transcription factors. But for now, this year concludes our brief introduction to Eukaryotic transcription of control and transcription factors, and I'll see you all in our next video.

2

concept

General Transcription Factors

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in this video, we're going to talk more details about general transcription factors. And so recall from our last lesson video that general transcription factors are called general transcription factors because they're required for the transcription of every gene in the genome of all jeans and so their general, because they are applied for all jeans. Now, general transcription factors are important for recruiting RNA preliminaries to the promoter region of a gene. And so, of course, when RNA polymerase is recruited to the promoter region, then transcription can proceed. Now what we haven't yet discussed is that the transcription initiation complex, which is commonly abbreviated as just T. I C, is really just the entire complex of all general transcription factors and the RNA preliminaries complex together. And so the transcription. All of the general transcription factors, along with the RNA preliminaries, come together to form the transcription initiation complex or the T. I C. And there is a specific sequence associated with eukaryotic organisms called the ta ta box, and the Tata box is literally just a sequence of A's and tease, or Adnan's and thigh means that repeat and is located in the promoter that recruits the t I see the transcription initiation complex. And so the Tata box is important for recruiting general transcription factors as well as the RNA polemics. And so if we take a look at our image down below notice again, we're showing you how general transcription factors will bind to the Tata box and the promoter and recruit RNA polymerase for transcription. And so notice again, over here on the left hand side, we're showing you this miniature map of our lesson and we're focused on transcription here, transcription all control, and part of that includes general transcription factors. And so notice again, we're showing you the DNA here and notice that within the promoter of the DNA, we have a specific region right here that has the t a t a repeats, and this is specifically the Tata box. And the Tata box is important for recruiting general transcription factors. And so these general transcription factors are represented as these little yellow structures that you see right here. And so the general transcription factors will bind to the Tata box within the promoter region and after the general transcription factors bind those general transcription factors are important for recruiting RNA preliminaries, allowing RNA polymerase to bind to the promoter region. And so once the RNA polymerase is bound to the Tata box within the promoter region, along with all of the general transcription factors, this is what we refer to as the transcription initiation complex or the T. I. C. And so, at this point, transcription can proceed and start to transcribe the coding sequence. And so this year concludes our brief introduction to general transcription factors, and as we move forward, we'll be able to compare this to specific transcription factors, which we'll talk about in our next video, so I'll see you all there.

3

concept

Specific Transcription Factors

3m

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in this video, we're going to talk more details about specific transcription factors, and so recall from our previous lesson videos that specific transcription factors are only going to be required for increasing the transcription of a specific genes. So specific transcription factors are not required for all jeans. They're only required for some specific genes. Now, these specific transcription factors they actually bind to these regions of DNA called control elements and so control elements are really just regions of non coding DNA, where specific transcription factors will bind. And really, there are two different types of control elements. There are distal control elements, and then there are proximal control elements. Now the distal control elements, as their name implies, are going to be located pretty far or distant from the promoter sequence. And really, a group of distal control elements are referred to as enhancers, And so an enhancer is going to be defined as a group of distal control elements where specific transcription factors will bind now proximal control elements. On the other hand, as their name implies, they're going to be located close or in close proximity to the promoter sequence. And so let's take a look at our image down below to get a better understanding of these specific transcription factors. And so specific transcription factors can bind either to distal or proximal control elements. And again, over here on the left hand side, we have our little miniature version of the map where you can see that transcription and transcription all regulation occurs within the nucleus of eukaryotic cells. And so notice over here, number one, What we're showing you are the distal control elements. And again, a group of distal control elements is referred to as an enhancer. And so you can see these three different regions right here that are these distal control elements and notice that they are some distance away from the promoter region of the gene. And so this little horizontal to slash bar here just represents that it is a significant distance away from the promoter region. So it's very, very far from the promoter. Um and then over here, number two, what we have are the proximal control elements and the proximal control elements. These two yellow regions here they are fairly close to the promoter region. And so what you'll notice is that it's these specific transcription factors highlighted here or or symbolize here with these, uh, pink shapes. Uh, these specific transcription factors can either bind to the distal or the proximal control elements, as you can see here, binding to the distal and then down below in our image here. Specific transcription factors binding to the proximal control elements. But the general transcription factors that we talked about in our previous lesson videos recall that they will bind specifically to the promoter region, and they are needed for all genes in general. And so basically, the idea here is that specific transcription factors can either bind to proximal control elements or distal control elements. And so this year concludes our brief lesson on specific transcription factors, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video

4

Problem

Problem

Regulatory segments of DNA that function to increase transcription levels in eukaryotes are called:

A

promoters.

B

silencers.

C

enhancers.

D

transcriptional start sites.

E

activators.

5

Problem

Problem

Which of the following statements correctly describes the primary difference between enhancers and proximal control elements?

A

Enhancers are transcription factors; proximal control elements are DNA sequences.

B

Enhancers increase transcription of specific genes; proximal control elements inhibit transcription of specific genes.

C

Enhancers are located thousands of nucleotides away from the promoter; proximal control elements are close to the promoter.

D

Enhancers are DNA sequences; proximal control elements are transcription factors.

6

Problem

Problem

Which of the following is NOT true regarding the differences of transcription in eukaryotes and prokaryotes?

A

Eukaryotes use multiple transcription factors to help initiate transcription.

B

Most eukaryotes have regulatory sites that are close to their promoters.

C

Most prokaryotes transcribe multiple genes under the regulation of a single operon.

D

Prokaryotic transcription factors usually interact directly with RNA polymerase while eukaryotic transcription factors do not.

7

Problem

Problem

Which of the following statements about transcription factors is incorrect:

A

The transcription initiation complex is composed of RNA polymerase, general and specific transcription factors.

B

General transcription factors help initiate transcription of all eukaryotic genes.

C

Specific transcription factors do not bind the promoter of a gene, but to control elements associated with the gene.

D

The transcription initiation complex associates with the TATA box of the promoter to begin transcription.

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