Figure 18.2 Regulation of gene - PowerPoint Presentation

Slide1

Slide2

Figure 18.2

Regulation

of gene

expression

Feedback

inhibition

Precursor

Genes that encode enzymes1, 2, and 3

Enzyme 1

Enzyme 2

Enzyme 3

trpE

trpD

trpC

trpB

trpA

Tryptophan

Regulation of enzymeactivity

(b) Regulation of enzymeproduction

–

–

Slide3

Figure 18.3

DNA

Promoter Regulatory gene

trpR

3′

trp

operon

trp

promoter

Genes of operon

trpB

trpA

mRNA

5′

trpE

trpD

trpC

trp

operator

RNA

polymerase

Stop codon

Start codon

mRNA

5′

Protein

Inactive

trp

repressor

E

D

C

B

A

Polypeptide

subunits

that make

up enzymes

for tryptophan

synthesis

(a) Tryptophan absent, repressor inactive, operon on.

DNA

trpR

3′

trpE

No

RNA

made

mRNA

5′

Protein

Active

trp

repressor

Tryptophan

(

corepressor

)

(b) Tryptophan present, repressor active, operon off.

Slide4

Figure 18.3a

Polypeptide

subunits

that make

up enzymes

for tryptophan

synthesis

DNA

Promoter Regulatory gene

trpR

3′

trp

operon

trp

promoter

Genes of operon

trpB

trpA

mRNA

5′

trpE

trpD

trpC

trp

operator

RNA

polymerase

Stop codon

Start codon

mRNA

5′

Protein

Inactive

trp

repressor

E

D

C

B

A

(a) Tryptophan absent, repressor inactive, operon on.

Slide5

Figure 18.3b

DNA

trpR

3′

trpE

No

RNA

made

mRNA

5′

Protein

Active

trp

repressor

Tryptophan

(

corepressor

)

(b) Tryptophan present, repressor active, operon off.

Slide6

Figure 18.4

Regulatory

gene

DNA

lac

I

3′

5′

Promoter

Operator

lacZ

No

RNA

made

mRNA

RNA

polymerase

Active

repressor

lac

operon

lac

I

lacZ

RNA

polymerase

3′

mRNA 5′

lacY

Stop codon

lacA

Protein

(a) Lactose absent, repressor active, operon off.

DNA

mRNA

5′

Protein

Allolactose

(inducer)

β

-

Galactosidase

Permease

Transacetylase

Inactive

lac

repressor

Enzymes for using lactose

(b) Lactose present, repressor inactive, operon on.

Start

codon

Slide7

Figure 18.4a

DNA

Regulatory

gene

lac

I

3′

5′

Promoter

Operator

lacZ

No

RNA

made

RNA

polymerase

Active

repressor

mRNA

Protein

(a) Lactose absent, repressor active, operon off.

Slide8

Figure 18.4b

lac

operon

DNA

lac

I

3′

5′

RNA polymerase

mRNA 5′

lacZ

lacY

lacA

Start

codon

mRNA

Protein

Inactive

lac

repressor

β

-

Galactosidase

Permease

Transacetylase

Allolactose

(inducer)

Enzymes for using lactose

(b) Lactose present, repressor inactive, operon on.

Stop

codon

Slide9

Figure 18.5

Promoter

DNA

lac

I

CRP-binding site

cAMP

Active

CRP

Inactive

CRP

Allolactose

Operator

lacZ

RNA

polymerase

binds and

transcribes

Inactive

lac

repressor

(a) Lactose present, glucose scarce (

cAMP

level high):

abundant

lac

mRNA synthesized.

DNA

lac

I

CRP-binding site

RNA polymerase

less likely to bind

Inactive

CRP

Inactive

lac

repressor

Promoter

Operator

lacZ

(b) Lactose present, glucose present (

cAMP

level low):

little

lac

mRNA synthesized.

Slide10

Figure 18.5a

Promoter

DNA

lac

I

CRP-binding site

cAMP

Active

CRP

Operator

lacZ

RNA

polymerase

binds and

transcribes

Inactive

lac

repressor

Inactive

CRP

Allolactose

(a) Lactose present, glucose scarce (

cAMP

level high):

abundant

lac

mRNA synthesized.

Slide11

Figure 18.5b

DNA

lac

I

CRP-binding site

Promoter

Operator

lacZ

RNA polymerase

less likely to bind

Inactive

CRP

Inactive

lac

repressor

(b) Lactose present, glucose present (

cAMP

level low):

little

lac

mRNA synthesized.

Slide12

Figure 18.6

Signal

Chromatin

Chromatin

modification:

DNA unpacking

DNA

Gene available for transcription

RNA

Cap

NUCLEUS

CYTOPLASM

Degradation

of mRNA

RNA processing

Tail

mRNA in

nucleus

Transport

to cytoplasm

Transcription

Exon

Primary

transcript

Intron

mRNA in

cytoplasm

Translation

Polypeptide

Protein processing

Active protein

Transport to cellular

destination

Cellular function

(such as enzymatic

activity or structural

support)

Degradation

of protein

Slide13

Figure 18.6a

Signal

Chromatin

Chromatin

modification:

DNA unpacking

DNA

Gene available for transcription

Transcription

Exon

RNA

Primary

transcript

Intron

RNA processing

Tail

mRNA in

nucleus

Cap

Transport

to cytoplasm

NUCLEUS

CYTOPLASM

Slide14

Figure 18.6b

CYTOPLASM

Degradation

of mRNA

mRNA in

cytoplasm

Translation

Polypeptide

Protein processing

Degradation

of protein

Active protein

Transport to cellular

destination

Cellular function

(such as enzymatic

activity or structural

support)

Slide15

Figure 18.7

Unacetylated histone tails

Histone

tails

Amino acids

available

for chemical

modification

Nucleosome

(end view)

(a) Histone tails protrude outward

from a nucleosome.

DNA double

helix

Acetylated

histone

tails

Nucleosome

DNA

Acetylation

DNA

Compact: DNA not

accessible for transcription

Looser: DNA accessible

for transcription

(b) Acetylation of histone tails promotes loose chromatin

structure that permits transcription.

Slide16

Figure 18.8

Enhancer (group of

distal control elements)

DNA

Upstream

Proximal

control elements

Transcription

start

site

Exon

Intron

Exon

Poly-A signal

sequence

Transcription

termination

region

Intron

Exon

Downstream

Poly-A

signal

Exon

Cleaved 3′ end

of primary

transcript

Promoter

Primary RNA

transcript

(pre-mRNA)

5′

Exon

Intron

Transcription

Exon

Intron

RNA

processing

Intron RNA

Coding segment

mRNA

G

P

P

P

5′ UTR

Start

codon

Stop

codon

3′ UTR

AAA

··

·

AAA

3′

5′ Cap

Poly-A

tail

Slide17

Figure 18.8a

Enhancer (group of

distal control elements)

DNA

Upstream

Proximal

control elements

Transcription

start site

Exon

Intron

Exon

Poly-A signal

sequence

Transcription

termination

region

Intron

Exon

Downstream

Promoter

Slide18

Figure 18.8b_1

Proximal

control elements

Transcription

start

site

DNA

Promoter

Exon

Intron

Exon

Poly-A signal

sequence

Intron

Exon

Slide19

Figure 18.8b_2

Proximal

control elements

Transcription

start

site

DNA

Promoter

Primary RNA

transcript

(pre-mRNA)

5′

Exon

Intron

Exon

Intron

Exon

Poly-A signal

sequence

Intron

Exon

Transcription

Poly-A

signal

Exon

Intron

Exon

Cleaved 3′

end of

primary

transcript

Slide20

Figure 18.8b_3

Proximal

control elements

Transcription

start

site

DNA

Promoter

Primary RNA

transcript

(pre-mRNA)

5′

Exon

Intron

Exon

Intron

Exon

Poly-A signal

sequence

Intron

Exon

Transcription

Poly-A

signal

Exon

Intron

Exon

RNA processing

Cleaved 3′

end of

primary

transcript

Intron RNA

Coding segment

mRNA

G

P

P

P

AAA

··

·

AAA

3′

5′

Cap

Start

codon

3′

UTR

Poly-A

tail

5

′ UTR

Stop

codon

Slide21

Figure 18.10_2

DNA

Activators

Distal control

element

Promoter

Gene

Enhancer

TATA

box

General transcription

factors

DNA-bending

protein

Group of

mediator proteins

Slide22

Figure 18.10_3

DNA

Activators

Distal control

element

Promoter

Gene

Enhancer

TATA

box

General transcription

factors

DNA-bending

protein

Group of

mediator proteins

RNA

polymerase

II

RNA

polymerase

II

Transcription

initiation complex

RNA synthesis

Slide23

Figure 18.11

DNA in both

cells

(activators

not shown)

Control

elements

Enhancer for

albumin gene

Promoter

Albumin gene

Enhancer for

crystallin gene

Promoter

Crystallin gene

Liver cell

Liver cell

nucleus

DNA in liver cell

Available

activators

DNA in lens cell

Lens cell

Lens cell

nucleus

Available

activators

Albumin gene not expressed

Albumin gene

expressed

Crystallin gene not expressed

Crystallin gene

expressed

Slide24

Figure 18.11a

DNA in both

cells

(activators

not shown)

Control

elements

Enhancer for

albumin gene

Albumin

gene

Enhancer for

crystallin gene

Promoter

Crystallin

gene

Promoter

Slide25

Figure 18.11b

DNA in liver cell

Liver cell

Liver cell

nucleus

Available

activators

Albumin gene

expressed

Crystallin

gene not expressed

Slide26

Figure 18.11c

DNA in lens cell

Lens cell

Lens cell

nucleus

Available

activators

Albumin gene not expressed

Crystallin

gene

expressed

Slide27

Figure 18.12

Chromosomes in the

interphase nucleus

(fluorescence micrograph)

Chromosome

territory

5

µ

m

Chromatin

loop

Transcription

factory

Slide28

Figure 18.13

Exons

DNA

1

2

3

4

5

Troponin T gene

Primary

RNA

transcript

1

2

3

4

5

RNA splicing

mRNA

1

2

3

5

OR

1

2

4

5

Slide29

Figure 18.14

miRNA

miRNA-

protein

complex

The

miRNA

binds to a target

mRNA

mRNA

OR

mRNA degraded

Translation blocked

If bases are complementary, mRNA is degraded (left); if

the match is less complete, translation is blocked (right).

1

2

Slide30

Figure 18.15

RNA transcripts

(red) produced.

Yeast enzyme

synthesizes strands

complementary to RNA

transcripts.

Double-stranded RNA

processed into

siRNAs

that associate with proteins.

The

siRNA

-protein complexes bind

RNA transcripts and become

tethered to centromere region.

The

siRNA

-protein

complexes recruit

histone-modifying

enzymes.

Formation of

heterochromatin at

the centromere.

Centromeric

DNA

RNA

polymerase

RNA

transcript

Sister

chromatids

(two DNA

molecules)

siRNA

-protein

complex

Centromeric DNA

Heterochromatin atthe centromere region

Chromatin-modifyingenzymes

1

2

3

4

5

6

Slide31

Figure 18.15a

Centromeric DNA

RNA transcripts

(red) produced.

Yeast enzyme

synthesizes strands

complementary to RNA

transcripts.

RNA

polymerase

RNA

transcript

Sister

chromatids

(two DNA

molecules)

Double-stranded RNA

processed into

siRNAs

that associate with proteins.

The

siRNA

-protein complexes bind

RNA transcripts and become

tethered to centromere region.

siRNA-protein

complex

1

2

3

4

Slide32

Figure 18.15b

The

siRNA

-protein

complexes recruit

histone-modifying

enzymes.

Centromeric

DNA

Formation of

heterochromatin at

the centromere.

Heterochromatin at

the centromere region

Chromatin-

modifying

enzymes

5

6

Slide33

Myoblasts are cells determined to form muscle cells and produce large amounts of muscle-specific proteins

MyoD

is a

“master regulatory gene” that encodes a transcription factor that commits the cell to becoming skeletal muscle

Some target genes for MyoD (protein) encode additional muscle-specific transcription factors© 2017 Pearson Education, Inc.

Slide34

Figure 18.18_2

Myoblast

(determined)

MyoD

protein

(transcription factor)

mRNA

OFFOFF

OFF

DNA

Embryonic

precursor cell

Nucleus

Master regulatory gene myoD

Other muscle-specific genes

Slide35

Figure 18.23

Proto-oncogene

Proto-oncogene

Proto-oncogene

Translocation or

transposition: gene

moved to new locus,

under new controls

Gene amplification:

multiple copies of the gene

Point mutation

within a control element

Point mutation

within the gene

New

promoter

Oncogene

Oncogene

Oncogene

Normal growth-

stimulating

protein in excess

Normal growth-stimulating

protein in excess

Normal growth-

stimulating protein

in excess

Hyperactive or

degradation-

resistant protein

Slide36

Figure 18.23a

Proto-oncogene

Translocation or

transposition:

gene moved to new

locus, under new

controls

New

promoter

Oncogene

Normal growth-

stimulating protein

in excess

Slide37

Figure 18.23b

Proto-oncogene

Gene amplification:

multiple copies of the gene

Normal growth-stimulating

protein in excess

Slide38

Figure 18.23c

Proto-oncogene

Point mutation

within a control element

Point mutation

within the gene

Oncogene

Oncogene

Normal growth-

stimulating protein

in excess

Hyperactive or

degradation-

resistant protein

Slide39

Figure 18.24

P

P

P

P

P

P

GTP

GTP

Growth

factor

G

protein

Transcription

factor (activator)

Protein

kinases

Receptor

Ras

NUCLEUS

Protein that

stimulates

the cell cycle

Normal cell

division

(a) Normal cell cycle–stimulating pathway.

MUTATION

Ras

Overexpression

of protein

NUCLEUS

Transcription

factor (activator)

Ras protein active with or

without growth factor.

Increased cell

division

(b) Mutant cell cycle–stimulating pathway.

3

4

5

6

2

1

Slide40

Figure 18.24a

P

P

P

P

P

P

Growth

factor

G

protein

Protein that

stimulates

the cell cycle

Ras

NUCLEUS

Transcription

factor (activator)

Receptor

Normal cell

division

(a) Normal cell cycle–stimulating pathway.

GTP

Protein

kinases

1

3

4

2

5

6

Slide41

Figure 18.24b

MUTATION

Ras

GTP

Overexpression

of protein

NUCLEUS

Transcription

factor (activator)

Increased cell

division

Ras protein active with or

without growth factor.

(b) Mutant cell cycle–stimulating pathway.

Slide42

Figure 18.25

Protein

kinases

Protein that

inhibits the

cell cycle

DNA damage

in genome

Active form

of p53

Transcription

Damaged DNA

is not replicated.

NUCLEUS

UV

light

No cell

division

(a) Normal cell cycle–inhibiting pathway

UV

light

DNA damage

in genome

MUTATION

Defective or

missing

transcription

factor

Inhibitory

protein

absent

Cell cycle is

not inhibited.

Increased

cell division

(b) Mutant cell cycle–inhibiting pathway

2

1

3

4

5

Slide43

Figure 18.25a

Protein

kinases

Protein that

inhibits the

cell cycle

DNA damage

in genome

Active form

of p53

Transcription

Damaged DNA

is not replicated.

NUCLEUS

UV

light

No cell

division

(a) Normal cell cycle–inhibiting pathway

2

1

3

4

5

Slide44

Figure 18.25b

UV

light

DNA damage

in genome

MUTATION

Defective or

missing

transcription

factor

Inhibitory

protein

absent

Cell cycle is

not inhibited.

Increased

cell division

(b) Mutant cell cycle–inhibiting pathway