Gene regulation:

1
Lecture 37

• Gene regulation
• Control of gene expression.
• (Prokaryotic cells)

2
Regulation of Gene Expression.
3
Type of Metabolism.
4
Turn-on a catabolic pathway.
5
Turn-off a anabolic pathway.
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Binding of a Regulator to an Operator.
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Gene regulation in prokaryotes 1. By positive
control a. with induction of gene expression b.
with repression of gene expression 2. By negative
control a. with induction of gene expression b.
with repression of gene expression.
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REGULATORS DNA-binding, allosteric proteins.
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(Prokaryotic) Operon.
Structural genes
P
O
A
B
C
R
DNA
RNA
active regulator
protein
E1
E2
E3
inactive regulator (Repressor,
Function
10
Tryptophan Operon.
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Tryptophan operon
Without tryptophan
polymerase
Structural genes
P
O
Z
Y
A
R
active regulator
Function
With tryptophan
P
O
Z
Y
A
R
inactive regulator
Tryptophan
active regulator
12
Lactose Operon.
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Lactose operon
Without lactose
P
O
Z
Y
A
R
active regulator
polymerase
With lactose
Structural genes
P
O
Z
Y
A
R
inactive regulator
active regulator
Function
Lactose
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(Prokaryotic) Operon.
Structural genes
P
O
A
B
C
R
DNA
RNA
active regulator
protein
E1
E2
E3
inactive regulator (Repressor,
Function
16
Gene regulation in prokaryotes 1. By positive
control a. with induction of gene expression b.
with repression of gene expression 2. By negative
control a. with induction of gene expression b.
with repression of gene expression.
17
Maltose operon positive control
Without maltose
P
O
Z
Y
A
R
inactive regulator
polymerase
With maltose
Structural genes
P
O
Z
Y
A
R
active regulator
inactive regulator
Function
Maltose
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Leucine operon negative control
Without leucine
polymerase
Structural genes
P
O
Z
Y
A
R
inactive regulator
Function
With leucine
P
O
Z
Y
A
R
active regulator
Leucine
inactive regulator
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Bacterial gene Operon.
20
Example Maltose Operon (Positive Control)
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Example Leucine Operon (Negative Control)
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Lactose Revisited two conditions.
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Lactose Revisited Lactose Regulator.
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Lactose Revisited CAP Regulator.
25
cAMP.
26
Fig. 14-6, p. 312
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Lactose Operon has two Operators
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Lactose Operon Induction Lactose Regulator and
CAP regulator. (Negative control Positive
Control)
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Lactose Operon Induction Lactose Regulator and
CAP regulator. (Negative control Positive
Control)
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Glucose low, cAMP high promotor activated
Glucose high, cAMP low, promotor not activated
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Glucose low Lactose not present
Glucose low Lactose present
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Lactose Operon.
GLU Lac Transcription
NO NO
YES NO
NO YES
YES YES
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Terminology
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Fig. 14-6, p. 312
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Transcription Factors DNA-binding Proteins.
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Three DNA-binding domains Helix-turn-Helix.
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Three DNA-binding domains Zn-finger.
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Zinc finger.
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Transcription Factor with 3 Zn-finger domains
bound to DNA.
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Three DNA-binding domains Leucine zipper
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Negative Control!
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(Helix-turn-helix)
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Lecture 38

• Gene regulation
• Eukaryotic cells,
• Transcription factors.

53
Eukaryotic Promotor / Basal Transcription Complex
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Regulation Eukaryotic Transcription
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Regulation of gene transcription activation of a
TF by phosphorylation.
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Protein Kinase.
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Regulation of gene transcription activation of a
TF by removal of inhibitor.
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Euchromatin and Hetero-chromatin
63
Common Bases
Methylated bases
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The End.