Transcriptional gene expression
Control of which genes are transcribed or the rate at which transcription occurs
Transcriptional gene expression specific mechanism in bacteria
- Nucleiod-associated proteins can enhance or prevent access to DNA
- Regulatory proteins
Post- transcriptional gene expression
- Control through modification of mRNA
- Splicing in eukaryotes
Post-transcriptional gene expression specific mechanism in bacteria
Most bacterial transcripts do not undergo post-transcriptional modifications like splicing
Translational gene expression
Control of frequency and speed at which mRNA transcripts are translated
Translational gene expression specific mechanism in bacteria
- Secondary structure in 3’ mRNA prevents degradation of transcript
- Translational repressors
- Small RNA binding to mRNA ca affect translational initiation
Post-translational gene expression
Control of the rate at which a protein becomes active or functional
Post-translational gene expression specific mechanism in bacteria
- Small molecule inhibitors
- phosphorylation, dephosphorylation, disulfide bond formation
- Protease activities
Class I activation - Bacterial transcription activator
Association of an activator protein upstream of the promoter region acts to recruit RNA polymerase to a specific promoter
Class II activation - Bacterial transcription activator
Activator binds very close to the promoter region where it can interact directly with domain 4 of the sigma factor
Activation by a promoter conformation change - Bacterial transcription activator
- Activators bind within the promoter region
- Acts to optimize the alignment of -35 and -10 elements of the promoter through a conformational change
- Facilitates recognition by RNA polymerase
Repression by steric hindrance - bacterial transcription repressor
Repressor protein binds to the promoter region and prevents the interaction of RNA polymerase with the promoter
Repression by looping - bacterial transcription repressor
- Repressor proteins can bind to regions upstream and downstream of the promoter and interact with each other
- Causes DNA to loop and prevents interaction with RNA polymerase
Repression by modulation of an activator - bacterial transcription repressor
- Repressor can interact with the activator
- Counteracts the attrition of RNA polymerase provided by the Activator
What happens when lactose is absent in the cell - Lac operon
After Lacl is transcribed and translated, it binds to operator region of the operon and prevents transcription of the downstream gene products
What happens when lactose is present in the cell - Lac operon
When lactose is present, it binds to the LacI repressor, preventing it from binding the operator so the lac operon genes can be transcribed
sigma factors role in response to stress - 1
Environmental stress signals for the production of σ⁽ᴱ⁾
sigma factors role in response to stress - 2
RNA polymerase with σ⁽ᴱ⁾ transcribes a regulon of genes that help the cell survive low pH by producing protective, protein-folding enzymes
sigma factors role in response to stress - 3
Stress to cell by low pH also impacts cytoplasmic functions
sigma factors role in response to stress - 4
- σ⁽ᴱ⁾-RNA polymerase activates transcription of σ⁽ᴴ⁾
- Promotes expression of genes that help the cell manage cytoplasmic stress
sigma factors role in response to stress - 5
σ⁽ᴴ⁾ up-regulates a gene that makes a protein enhancing translation of another σ factor, σ⁽ˢ⁾
sigma factors role in response to stress - 6
σ⁽ˢ⁾ directs transcription of genes that help the cell handle nutrient decreases caused by stress
Prokaryotic translation
- Transcription and translation occur simultaneously in the cytoplasm
- Connects regulation of gene expression mainly to transcription
Eukaryotic translation
- Eukaryotic transcription and RNA processing take place in the nucleus and translation takes place in cytoplasm
- Translation has extensive regulatory mechanisms
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Module 1: Section 124
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Module 1: Section 236
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Module 2: Section 1A26
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Module 2: Section 1B54
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Module 2: Section 1C8
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Module 2: Section 1D7
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Module 2: Section 2A16
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Module 2: Section 2B6
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Module 2: Section 2C5
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Module 2: Section 2D12
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Module 3: Section 1A15
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Module 3: Section 1B19
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Module 3: Section 1C16
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Module 3: Section 2A18
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Module 3: Section 2B22
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Module 3: Section 2C31
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Module 3: Section 2D23
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Module 3: Section 2E14
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Module 4: Section 1A24
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Module 4: Section 1B24
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Module 4: Section 2A15
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Module 4: Section 2B14
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Module 4: Section 3A34
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Module 4: Section 3B31
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Module 4: Section 3C21
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Module 5: Section 1A15
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Module 5: Section 1B9
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Module 5: Section 1C14
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Module 5: Section 2A30
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Module 5: Section 2B13
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Module 5: Section 2C32
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Module 6: Section 1A15
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Module 6: Section 1B24
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Module 6: Section 1C14
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Module 6: Section 2A14
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Module 6: Section 2B32
