chapter 6 regulation of prokaryotic gene expression
DESCRIPTION
Chapter 6 Regulation of Prokaryotic Gene Expression. 6.1 Overview 1. What are Gene Expression and Regulation? (1) Gene expression. Constitutive Expression Regulated/Adaptive Expression. (2) Gene regulation/control. 2. Influencing factors Nutritional status - PowerPoint PPT PresentationTRANSCRIPT
Chapter 6
Regulation of Prokaryotic Gene Expression
6.1 Overview
1. What are Gene Expression and Regula
tion?
(1) Gene expression Constitutive Expression Regulated/Adaptive Expression
(2) Gene regulation/control
2. Influencing factors
Nutritional status
Environmental factors
Hormone level
Developmental stage
3. Operon
(1) What is an operon?
(2) Operon types
Inducible operon
Repressible operon
(3) Gene regulation of operon
Negative regulation
Positive regulation
负控诱导系统 正控诱导系统
正控阻遏系统 负控阻遏系统
1. Organization of lac operon
lacI
Regulatory gene
lacZ lacY lacA DNA
mRNA
β -GalactosidasePermease
Transacetylase
Protein
Structural Genes
PlacI PlacOlac
repressor
6.2 The Regulation of lac Operon
3. Positive control of lac operon cAMP CAP (catabolite activator protein) or cAMP receptor protein (CRP)
4. Negative contral of lac operon
p t
pt
lacI lacZ lacY lacA
Repressor -galactosidasetranscripts
Permease Transacetylase
1. + Inducer (lactose/ allolactose)
o
InducedRepressor cannot bind
2. No Inducerp t
lacI lacZ lacY lacA
o
RepressedRepressor binds to laco
transcript
Animation
1. Organization of trp operon
6.3 The Regulation of trp Operon
2. The Repression of trp Operon
trpR → Repressor
Corepressor
Attenuator
3. The Attenuation Mechanism of trp Operon
Mechanism of Attenuation When Ribosome reaches Trp codon
Trp is scarce Trp is aboudant
Attenuation model in Trp starved cells.
Attenuation model in Trp non-starved cells
Animation
5. Generality of Attenuation
1. The Regulation of ara Operon
(1) organization
6.4 The Regulation of Other Operons
P t
Pt
araC araB araA araD
Activator/ Repressor
I1 I2
AraC dimer
CRP
O2 O1
Arabinose absent →Negative control
araB A D
O1 CRP araI
araC
O2
PCPBAD
Blocked
Arabinose present → Positive control
araB A D
O1 CRP araI
araC
PCPBAD
O2
Transcription
2. The Regulation of rRNA Operon
(1) organization
6.5 Riboswitches
1. What is a riboswitch?
Riboswitches have two important domains:
an aptamer
an expression platform
2. Mechanism of Riboswitches
(1) Inhibition of Translation Initiation
(2) Transcription termination
(3) Auto-cleavage
3. Tempting Targets
4. Riboswitches and the RNA World hypothesis
5. Riboswitches as Antibiotic Targets
Blount KF, Breaker RR. Riboswitches as antibacterial drug targets". Nat Biotechnol, 2006, 24 (12): 1558-64.
Brantl, S. Bacterial gene regulation: from transcription attenuation to riboswitches and ribozymes. Trends Microbiol, 2004, 12:473-475.
Mandal, M. and R. R. Breaker. Gene Regulation by Riboswitches. Nat Rev Mol Cell Biol, 2004, 5:451-463.
6.6 Time Regulation
Different sigma factors recognize different promoters and thus, the availability of sigma factors can regulate the transcription of genes associated with these promoters.
1. Time Regulation of Sigma Factors
Early
Middle
Late
Uncommitted.
2. Time Regulation of λ phage
Committed.
Lysogeny
Lysis
Execution
Lysogeny
Lysis
1. Translation Initiation of Regulation
(1) Ribosome binding site (rbs)
(2) SD sequencing
(3) mRNA secondary structure
(4) Initiational codon
2. Regulation of Rare Codon
3. Transcriptional Regulation of Overlapping Gene
4. Translational Repression
6.7 Post-Transcriptional Regulation
Summary1. Concepts
Gene Expression Operon Attenuator
Constitutive Expression
Inducible Operon Attenuation
Regulated Expression Repressible Operon Riboswitch
Gene Regulation
2. Differences between inducible operon and repressible operon3. The regulation mechanism of lac operon4. The regulation mechanism of trp operon (attenuation)5. The regulation mechanism of ara operon6. The regulation mechanism of riboswitches