Transcription Initiation in Eukaryotes

Summary

This video delves into the intricate process of transcription initiation in eukaryotes, focusing on the pivotal role of RNA polymerase II and the general transcription factors known as TF IIs. It explains how TF II D, with the aid of TF II A, recognizes and binds to the TATA box, initiating a cascade of factor recruitments, including TF II B, E, F, and H. Highlighting the importance of TF II H's ATPase and helicase activities, the video illustrates the formation of the minimal pre-initiation complex and the phosphorylation dynamics of RNA polymerase II's CTD. It concludes with the initiation of transcription and the role of elongation factors, providing a comprehensive understanding of gene expression regulation in eukaryotic cells.

Takeaways

• 🔬 RNA polymerase II is responsible for transcribing all protein-coding genes in eukaryotes.
• 🧬 General Transcription Factors (TF II), including TF II D, A, B, F, E, H, play crucial roles in the transcription initiation process.
• 🎯 The TATA box is an important promoter sequence recognized by TF II D and TF II A for transcription initiation.
• 🔄 TF II D binding to the TATA box initiates the recruitment of other transcription factors, forming a complex.
• 🔗 TF II B is recruited to the complex by TF II D, which in turn recruits RNA polymerase II and TF II F.
• 🌀 TF II E and TF II H are the last to join, with TF II H possessing ATPase and helicase activities, essential for unwinding DNA.
• 🔋 The CTD of RNA polymerase II undergoes dynamic phosphorylation at different stages of transcription, affecting its function.
• 🌡 The phosphorylation at Ser 5 during initiation recruits the capping enzyme, while Ser 5 and Ser 2 are phosphorylated during elongation.
• 🔬 The assembly of RNA polymerase II with the six general transcription factors forms the minimal pre-initiation complex.
• 🔄 Regulatory Transcription factors such as CBF, CREB, SP1, and others modulate the transcription process.
• 📝 The transcription process involves the addition of nucleotides to the transcription machinery, leading to RNA synthesis by RNA polymerase II.

Q & A

What is the primary enzyme responsible for transcribing protein-coding genes in eukaryotes?

RNA polymerase II is the primary enzyme responsible for transcribing all protein-coding genes in eukaryotes.

What are the general transcription factors involved in eukaryotic transcription initiation?

The general transcription factors involved in eukaryotic transcription initiation are the TF II factors, which include TF II D, A, B, F, E, and H.

What is the role of the TATA box in eukaryotic transcription initiation?

The TATA box is an important consensus sequence in the promoter region of DNA, recognized by the TBP region of TF II D, which aids in the binding of the transcription machinery to the DNA.

How does TF II A assist in the transcription initiation process?

TF II A aids in the recognition of the TATA box by TF II D, which is a critical step in the assembly of the transcription initiation complex.

What is the function of TF II B in the transcription initiation complex?

TF II B binds to the complex after TF II D has bound to the TATA box and it helps in recruiting RNA polymerase II and TF II F to the complex.

What is the significance of the CTD of RNA polymerase II during transcription?

The CTD of RNA polymerase II undergoes dynamic phosphorylation throughout the transcription process, which is crucial for the recruitment of the capping enzyme and the regulation of transcription.

What is the role of TF II H in the transcription initiation?

TF II H is an important transcription factor with ATPase and helicase activity, which unwinds the DNA at the start point and phosphorylates the CTD of RNA polymerase II.

What happens to the DNA structure during transcription initiation due to TF II H?

Due to the action of TF II H, the DNA is unwound, providing an open form of DNA necessary for the RNA polymerase to initiate transcription.

What constitutes the minimal pre-initiation complex in eukaryotic transcription?

The minimal pre-initiation complex in eukaryotic transcription is formed by the assembly of RNA polymerase II with the six general transcription factors.

Are there any regulatory transcription factors that influence the transcription initiation process?

Yes, there are regulatory transcription factors like CBF, CREB, and SP1 that play a role in modulating the transcription initiation process.

How does the RNA polymerase II synthesize the RNA molecule during transcription?

RNA polymerase II moves along the DNA template from the 3' to 5' strand and synthesizes the RNA molecule with the help of elongation factors.

Outlines

00:00

🔬 Transcription Initiation in Eukaryotes

This paragraph introduces the topic of transcription initiation in eukaryotes, focusing on the role of RNA polymerase II and the general transcription factors known as TF II factors. It explains that RNA polymerase II is responsible for transcribing all protein-coding genes and requires assistance from various TF II factors, including TF II D, A, B, F, E, and H. The paragraph also mentions the importance of the TATA box and other consensus sequences in the promoter region of DNA. The process begins with TF II D recognizing and binding to the TATA box, which is aided by TF II A. This binding event recruits TF II B, and subsequently, RNA polymerase II and TF II F join the complex, facilitated by TF II B. The paragraph concludes with the description of the assembly of the minimal pre-initiation complex, which includes RNA polymerase II and the six general transcription factors.

Keywords

💡Transcription Initiation

Transcription initiation is the process by which RNA synthesis begins in eukaryotic cells. It is a crucial step in gene expression, where the genetic information stored in DNA is copied into RNA by RNA polymerase II. In the video, this concept is central to understanding how protein-coding genes are activated and how the transcription machinery assembles at the start site.

💡RNA polymerase II

RNA polymerase II is the enzyme responsible for transcribing DNA into messenger RNA (mRNA) in eukaryotes, which is then translated into proteins. The video emphasizes its role in binding to the promoter region of protein-coding genes, facilitated by various transcription factors, to initiate the transcription process.

💡General Transcription Factors

General Transcription Factors (GTFs) are proteins that assist RNA polymerase II in the initiation of transcription. The TF II factors mentioned in the video, such as TF II D, A, B, F, E, H, are essential for assembling the pre-initiation complex. They help in recognizing specific DNA sequences and recruiting RNA polymerase II to the transcription start site.

💡TATA Box

The TATA Box is a DNA sequence found in the promoter region of many eukaryotic genes. It is recognized by the TATA-binding protein (TBP), which is part of the TF II D complex. The video describes how TF II D, with its TBP region, binds to the TATA box, marking one of the initial steps in transcription initiation.

💡Transcription Start Point

The Transcription Start Point is the exact location on the DNA where RNA polymerase begins to synthesize RNA. The video script mentions that this point is marked on the DNA and is in proximity to the TATA box, indicating where the RNA synthesis will commence.

💡Promoter

A promoter is a DNA sequence that signals the starting point for transcription and helps in the recruitment of RNA polymerase and transcription factors. The video explains that the TATA box is one of several consensus sequences found within promoters that are important for initiating transcription.

💡TF II D

TF II D is a general transcription factor that includes the TATA box-binding protein (TBP). In the video, TF II D is highlighted as the first factor to bind to the DNA, recognizing and binding to the TATA box, which is a critical step in the assembly of the transcription initiation complex.

💡TF II B

TF II B is another general transcription factor that plays a role in recruiting RNA polymerase II to the transcription complex. As described in the video, after TF II D binds to the TATA box, TF II B is recruited, which then helps in the binding of RNA polymerase II and TF II F to the complex.

💡TF II H

TF II H is a general transcription factor with ATPase and helicase activity, which is vital for the initiation of transcription. The video explains that TF II H unwinds the DNA at the start point and phosphorylates the C-terminal domain (CTD) of RNA polymerase II, which is essential for the progression of transcription.

💡CTD Phosphorylation

The C-terminal domain (CTD) of RNA polymerase II undergoes dynamic phosphorylation during the transcription process. The video describes how the CTD is phosphorylated at different stages of transcription, with Ser5 phosphorylation occurring at initiation to recruit the capping enzyme, and both Ser5 and Ser2 during elongation, with only Ser2 phosphorylated at termination.

💡Pre-Initiation Complex

The Pre-Initiation Complex is a multi-protein assembly that includes RNA polymerase II and the general transcription factors. The video mentions that the assembly of these components constitutes the minimal pre-initiation complex, which is necessary for the initiation of transcription.

Highlights

RNA polymerase II transcribes all protein coding genes in eukaryotes.

General Transcription Factors, TF II factors, are essential for transcription in eukaryotes.

TF II D, A, B, F, E, H are key components of the transcription process.

The TATA Box is an important promoter sequence recognized by TF II D and TF II A.

TF II D binding to the TATA box is a crucial step in transcription initiation.

TF II B recruitment follows TF II D binding, forming a complex with RNA polymerase.

RNA polymerase II and TF II F are recruited to the complex by TF II B.

TF II E and TF II H are additional factors that join the transcription complex.

TF II H has ATPase and helicase activity, which is vital for DNA unwinding.

Phosphorylation of the CTD of RNA polymerase II is dynamic and stage-specific.

Serine 5 phosphorylation at the initiation stage recruits the capping enzyme.

During elongation, both serine 5 and serine 2 are phosphorylated.

Serine 2 phosphorylation occurs only during the termination stage.

The assembly of RNA polymerase II with the six general transcription factors forms the minimal Pre-Initiation Complex.

Regulatory Transcription factors like CBF, CREB, SP1 play a role in controlling transcription.

Nucleotides are added to the transcription machinery, initiating the transcription process.

RNA polymerase II moves along the 3' to 5' strand to synthesize the RNA molecule with the help of elongation factors.

Transcripts

In the series of videos we have been discussing abt the Transcription in Prokaryotes and we

also discussed the proteins and enzymes in Eukaryotic transcription if u want to watch

that video first the link is in the description.

Now in this video we will be discussing abt the Transcription Initiation in Eukaryotes.

Before we get into the detailed mechanism we know it is the RNA polymerase II that transcribes

all protein coding genes and we also need several General Transcription Factors called

the TF II factors that includes TF II D , A , B , F , E , H

Now lets get to the transcription initiation, here in this diagram we can we the DNA having

TATA Box and a Transcription Start Point.

There are several other consensus sequences on DNA of which this TATA BOX is one of the

important sequences of Promoter. Other Consenses sequences are shown in the diagram displayed

here ( u can watch the complete video of Eukaryotic promoter , linked in the description )

Going forward now , we see we have TF II D first in the run, it has got TBP region which

is able to recognise TATA box and this recognition of TATA box is aided another Transcription

factor TF II A. So from here TF II D recognises the TATA box on DNA and binds to it as shown

in the diagram. and the binding of TFII D to the TATA box

recruits another Transcription factor TF II B , which comes in and joins the complex .

Now we have RNA Polymerase shown in the diagram below which marks it enters along with the

TRANSCRIPTION Factor II F . The RNA Polymerase and TF II F is recruited to the complex by

the TF II B and finally we have another two factors TF II E and TF II H .

First of all TF II E joins in and then this E factor inturn recruits TF II H.

This TF II H is important Transcription factor , since it has ATpase and Helicase activity.

It unwinds DNA at start point and also phosphorylates the CTD of RNA polymerase II.

The CTD of RNA polymerase has dynamic phosphorlyation through out the Transcription process. It

is shown in the diagram , at initiation stage Ser 5 is phosphorylated which recruits capping

enzyme , while as during elongation ser 5 as well as ser 2 is phosphorylated and at

the end during termination only serine 2 is phosphorylated.

Now getting back to the mechanism , we see the unwinding has occurred due to TF II H

, which gives us open form DNA as shown in the diagram.

The assembly of RNA polymerase II with the 6 General Transcription factors constitutes

us the MINIMAL Pre Initiation Complex.

There are other Regulatory Transcription factors which regulated the transcription , like we

have CBF , CREB , SP1

More over to drive the Transcription nucleotides are added to the transcription machinery where

first of all some factors disassemble and then this Polymerase can initiate the Transcription.

the RNA Poly II moves forward on 3 prime to 5 prime strand and synthesises RNA molecule….by

the help of elongation factors.

So this is how Transcription is initiated in the eukaryotes by the RNA polymerase enzyme

along with the T Fs.

I hope You like the video if u like it give it a thumbs up , do consider supporting my

work on Patreon and also make sure to subscribe to this channel. Thanks