GROUP 2: TRANSCRIPTIONAL REGULATION

Transcription Regulation

An essential process that helps cells respond to intra- and extracellular signals. It plays a key role in shaping a cell’s identity during development, keeping that identity stable throughout its life, and coordinating various cellular functions. In simpler terms, it controls how much a gene is expressed.

Prokaryotic Regulation 

In bacteria, genes are often clustered in groups, such that genes that need to be

expressed at the same time are next to each other and all of them are controlled as a single unit by the same promoter.

Promoter

In prokaryotic regulation this is where the RNA polymerase must bind to begin transcription

Repressor

In prokaryotic regulation, protein that can physically block RNA polymerase from transcribing genes

Operator

In prokaryotic regulation, the site where the repressor binds to

Lac operon

Is an example of a group of genes that encode proteins needed for the uptake and breakdown of the sugar lactose.

Single promoter

The three genes of the lac operon are controlled by a?

Bacterial cells

These cells generally prefer to use glucose for their energy needs, but if glucose is unavailable, and lactose is present, they will take up lactose and break it down for energy.

Repressor

In order for transcription to occur, this must be removed from the operator to clear the path for RNA polymerase

Eukaryotic Transcription Regulation

Like prokaryotic cells, the transcription of genes requires the action of an RNA polymerase to bind to a DNA sequence of a gene in order to initiate transcription. However, unlike prokaryotic cells, the eukaryotic RNA polymerase requires other proteins, or transcription factors, to facilitate transcription initiation

Promoter region

This region is immediately upstream of the coding sequence. This region can be short (only a few nucleotides in length) or quite long (hundreds of nucleotides long).

Gene-specific 

The length of the promoter is _________ and can differ dramatically between genes. 

Promoter

Its purpose is to bind transcription factors that control the initiation of transcription

25 to 35 bases 

Within the core promoter region, _________ bases upstream of the transcriptional start site, resides the TATA box

TATA Box

The binding site for a protein complex called Transcription Factor II D (TFIID) which contains a TATA-binding protein and has the consensus sequence of 5’-TATAAA-3’

Transcription Factor II D

TATA box is the binding site for a protein complex called? 

TFIID

Transcription Factor II D is also written as?

5’-TATAAA-3’

TATA box - the binding site for a protein complex called Transcription Factor II D (TFIID) which contains a TATA-binding protein and has the consensus sequence of? 

TFIIB, TFIIE, TFIIF, TFIIH

Binding TFIID recruits other transcription factors, including:

Transcription Factors

Respond to environmental stimuli that cause the proteins to find their binding sites and initiate transcription of the gene that is needed.

Hsf1

A prominent example of a eukaryotic transcription factor responding to environmental stimuli is

Hsf1

When a cell experiences heat stress, this stimuli is activated, binds to DNA, and promotes the transcription of genes encoding heat shock proteins, which protect the cell from damage.

Enhancers

Are short regions of DNA that stimulate the transcription of specific genes despite being thousands of base pairs away. Also works by serving as binding sites for activator proteins and transcription factors, which then helps recruit the transcription machinery like RNA polymerase to the gene’s promoter. Common in eukaryotic genomes but rare in bacterial genomes

Simian virus 40 genome

The first enhancer to be discovered that stimulates transcription of eukaryotic genes was in a 366-bp fragment of the?

SV40

Simian virus is also written as?

Walter Schaffner (1981)

Simian virus 40 (SV40) genome was identified by? (Include the year)

Low basic level

Without an enhancer, a gene is usually transcribed at a?

Gene is transcribed 

When an enhancer is added, it can greatly increase how much the ________

Before (upstream) or after (downstream)

Enhancers can work even when they are placed far from the gene, either?

Repressors 

This in Eukaryotic transcription regulation are proteins that decrease or block gene expression by preventing transcription

Promoter region of a gene

Repressors bind to specific DNA sequences, often near or at the 

mRNA

Repressors bind to specific DNA sequences, often near or at the promoter region of a gene, and inhibit the binding or activity of RNA polymerase, preventing the production of?

Repression domains

This remains functional even when fused to different DNA-binding domains and work by interacting with other proteins.

Direct blocking, Chromatin modification, Competition

Three ways repressors work:

Direct blocking

The repressor physically blocks RNA polymerase from accessing the gene.

Chromatin modification 

The repressor recruits other proteins (like histone deacetylases) that tighten DNA packaging, making the gene less accessible.

Competition

Repressors compete with activators for the same DNA binding site.