Regulation of Gene Expression

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6

Fig. 18-8-2

Enhancer

(distal control elements)

Proximal

control elements

Poly-A signal

sequence

Termination

region

Downstream

Promoter

Upstream

DNA

Exon

Exon

Exon

Intron

Intron

Cleaved 3 end

of primary

transcript

Primary RNA

transcript

Poly-A

signal

Transcription

5

Exon

Exon

Exon

Intron

Intron

Slide 37

Fig. 18-8-3

Enhancer

(distal control elements)

Proximal

control elements

Poly-A signal

sequence

Termination

region

Downstream

Promoter

Upstream

DNA

Exon

Exon

Exon

Intron

Intron

Exon

Exon

Exon

Intron

Intron

Cleaved 3 end

of primary

transcript

Primary RNA

transcript

Poly-A

signal

Transcription

5

RNA processing

Intron RNA

Coding segment

mRNA

5 Cap

5 UTR

Start

codon

Stop

codon

3 UTR

Poly-A

tail

3

Slide 38

The Roles of Transcription Factors

To initiate transcription, eukaryotic RNA polymerase requires the assistance of proteins called transcription factors

General transcription factors are essential for the transcription of all protein-coding genes

In eukaryotes, high levels of transcription of particular genes depend on control elements interacting with specific transcription factors

Slide 39

Proximal control elements are located close to the promoter

Distal control elements, groups of which are called enhancers, may be far away from a gene or even located in an intron

Enhancers and Specific Transcription Factors

Slide 40

An activator is a protein that binds to an enhancer and stimulates transcription of a gene

Bound activators cause mediator proteins to interact with proteins at the promoter

Animation: Initiation of Transcription

Slide 41

Fig. 18-9-1

Enhancer

TATA

box

Promoter

Activators

DNA

Gene

Distal control

element

Slide 42

Fig. 18-9-2

Enhancer

TATA

box

Promoter

Activators

DNA

Gene

Distal control

element

Group of

mediator proteins

DNA-bending

protein

General

transcription

factors

Slide 43