Detailed Notes on Mechanisms of Post-Transcriptional Regulation in Bacteria

intro

the control of gene expression at the RNA level

after transcription of DNA into messenger RNA (mRNA),

before translation into proteins.

layer of regulation

allows bacteria to respond rapidly to environmental changes and optimize resource usage.

mechanisms of post-transcriptional regulation in bacteria include:

RNA Stability and Degradation

Riboswitches

Small Regulatory RNAs (sRNAs)

Attenuation

Translation Regulation

intro

Post-transcriptional regulation in bacteria refers to

the control of gene expression at the RNA level

after the transcription of DNA into messenger RNA (mRNA),

but before translation into proteins.

intro

This layer of regulation allows bacteria to

respond rapidly to environmental changes and optimize resource usage.

intro

The major mechanisms of post-transcriptional regulation in bacteria include:

RNA Stability and Degradation

riboswitches

RNA Stability and Degradation

Attenuation

Translation Regulation

main point 1 listed

mRNA half-life

RNases

Specific secondary structures in mRNA,

main point 1 RNA Stability and Degradation

mRNA half-life is

a critical determinant of gene expression.

main point 1 RNA Stability and Degradation

Bacterial mRNAs typically have

short half-lives, ranging from seconds to a few minutes.

main point 1 1. RNA Stability and Degradation

RNases are what in this process

key enzymes

main point 1 1. RNA Stability and Degradation

RNases are key enzymes in this process:

• RNase E

• PNPase, RNase II, and RNase R

main point 1 1. RNA Stability and Degradation

RNases are key enzymes in this process:

• RNase E

• initiates endonucleolytic cleavage.

main point 1 RNA stability and degradation

RNases are key enzymes in this process:

• PNPase, RNase II, and RNase R

• perform exonucleolytic degradation.

main point 1 RNA stability and degradation

Specific secondary structures in mRNA, such as stem-loops, can

shield the transcript from RNases, increasing its stability.

main point 1 RNA stability and degradation

Specific secondary structures in mRNA, such as

stem-loops,

main point 2

Riboswitches

listed

cis-acting regulatory elements

parts - aptamer domain and expression platform

binding = conformational change

TPP riboswitch

main point 2

Riboswitches

Riboswitches are cis-acting regulatory elements located

in the 5′ untranslated region (5′ UTR) of mRNAs.

main point 2

Riboswitches

They consist of two parts:

the aptamer domain, which binds a small metabolite,

the expression platform, which alters gene expression.

main point 2

Riboswitches

Binding of the ligand causes

conformational changes that affect transcription termination or translation initiation.

main point 2

Riboswitches

Example:

The TPP (thiamine pyrophosphate) riboswitch regulates genes involved in thiamine biosynthesis.

main point 3

Small Regulatory RNAs (sRNAs)

listed

short non coding RNAs

base pair with target mRNA

translation initiation

mRNA stability

Hfq

RyhB sRNA

main point 3

Small Regulatory RNAs (sRNAs)

sRNAs are

short, non-coding RNAs (50–250 nucleotides)

that regulate gene expression post-transcriptionally.

main point 3

Small Regulatory RNAs (sRNAs)

They typically act by

base-pairing with target mRNAs,

main point 3

Small Regulatory RNAs (sRNAs)

They typically act by base-pairing with target mRNAs, affecting:

• Translation initiation (by blocking or exposing the ribosome binding site),

• mRNA stability (by recruiting RNases or protecting from degradation).

main point 3

Small Regulatory RNAs (sRNAs)

Hfq,

an RNA chaperone protein,

often facilitates sRNA-mRNA interactions.

main point 3

Small Regulatory RNAs (sRNAs)

Example: RyhB sRNA

regulates iron metabolism in E. coli by repressing synthesis of iron-using proteins.

main point 4

Attenuation

listed

premature termination

respond to translational cues

secondry structures - leader sequence

amino acid - operon biosynthesis -trp

abundant - leader peptide - terminator hairpin

scarce - ribosome stalling - mRNA folding

main point 4

Attenuation

Attenuation is

a regulatory mechanism

involves premature termination of transcription

in response to translational cues.

main point 4

Attenuation

It often relies on

the formation of alternative secondary structures in the mRNA leader sequence.

main point 4

Attenuation

Common in amino acid biosynthesis operons such as

the trp operon in E. coli

main point 4

Attenuation

Common in

amino acid biosynthesis operons

main point 4

Attenuation

Common in amino acid biosynthesis operons such as the trp operon in E. coli:

• When tryptophan is abundant,

• a leader peptide is translated efficiently,

• causing formation of a transcription terminator hairpin.

main point 4

Attenuation

Common in amino acid biosynthesis operons such as the trp operon in E. coli:

When tryptophan is scarce,

ribosome stalling alters mRNA folding,

allowing transcription to continue.

main point 5

Translation Regulation

listed

rna thermometers

heat shock genes

ribosome binding site (RBS) accessibility

main point 5

Translation Regulation

Regulation at the translation level involves:

RNA thermometers

Ribosome binding site (RBS) accessibility

main point 5

Translation Regulation

Regulation at the translation level involves:

RNA thermometers:

Structures that melt at higher temperatures to allow translation.

main point 5

Translation Regulation

Regulation at the translation level involves:

RNA thermometers:

example

Heat-shock genes activated by melting of RNA structures in the 5′ UTR.

main point 5

Translation Regulation

Regulation at the translation level involves:

• Ribosome binding site (RBS) accessibility:

• Structures in the mRNA

• can hide or expose the Shine-Dalgarno sequence,

  • modulating translation initiation.

Conclusion:

list

Post-transcriptional regulation in bacteria

versatile and energy-efficient strategy

fine-tunes gene expression

response to environmental signals.

mechanisms

• control of mRNA stability,

• riboswitch-mediated regulation,

• sRNA interference,

• transcription attenuation,

• translational regulation.

Conclusion:

Post-transcriptional regulation in bacteria is that

a versatile and energy-efficient strategy

Conclusion:

Post-transcriptional regulation in bacteria is a versatile and energy-efficient strategy that

fine-tunes gene expression in response to environmental signals.

Conclusion:

Post-transcriptional regulation in bacteria is a versatile and energy-efficient strategy that fine-tunes gene expression in response to environmental signals.

It includes mechanisms such as

control of mRNA stability, riboswitch-mediated regulation, sRNA interference, transcription attenuation, and translational regulation.

Conclusion:

Post-transcriptional regulation in bacteria is a versatile and energy-efficient strategy that fine-tunes gene expression in response to environmental signals.

It includes mechanisms such as control of mRNA stability, riboswitch-mediated regulation, sRNA interference, transcription attenuation, and translational regulation.

Together, these mechanisms

enable bacteria to adapt rapidly and precisely to changing conditions.

INTRODUCTION

Flashcard 1
Q: What is post-transcriptional regulation in bacteria?
A:

Regulation of gene expression at the RNA level after transcription but before translation.

INTRODUCTION Flashcard 2
Q: Why is post-transcriptional regulation important in bacteria?
A:

It enables rapid response to environmental changes and efficient resource use.

RNA STABILITY AND DEGRADATION

Flashcard 5
Q: How do mRNA secondary structures affect degradation?
A:

Structures like stem-loops protect RNA from RNase digestion, increasing stability.

🟨 1. RNA STABILITY AND DEGRADATION

Flashcard 4
Q: Which RNases are involved in RNA degradation?
A:

RNase E (endonucleolytic), PNPase, RNase II, and RNase R (exonucleolytic).

🟨 1. RNA STABILITY AND DEGRADATION

Flashcard 3
Q: How does mRNA half-life affect gene expression?
A:

Short mRNA half-lives limit protein production, allowing tight regulation.

2. RIBOSWITCHES

Flashcard 9
Q: Example of a riboswitch and its function?
A:

TPP riboswitch regulates thiamine biosynthesis genes.

2. RIBOSWITCHES

Flashcard 8
Q: How do riboswitches regulate gene expression?
A:

Ligand binding induces structural changes that affect transcription or translation.

2. RIBOSWITCHES

Flashcard 7
Q: What are the two components of a riboswitch?
A:

Aptamer domain (binds ligand) and expression platform (modulates expression).

2. RIBOSWITCHES

Flashcard 6
Q: Where are riboswitches located?
A:

In the 5′ untranslated region (5′ UTR) of mRNAs.

3. SMALL REGULATORY RNAs (sRNAs)

Flashcard 13
Q: Example of an sRNA and its role?
A:.

RyhB represses iron-using proteins in E. coli during iron limitation

3. SMALL REGULATORY RNAs (sRNAs)

Flashcard 12
Q: What protein assists sRNA-mRNA interactions?
A:

Hfq, an RNA chaperone.

3. SMALL REGULATORY RNAs (sRNAs)

Flashcard 11
Q: How do sRNAs regulate gene expression?
A:

By base-pairing with mRNAs to affect translation initiation or mRNA stability.

3. SMALL REGULATORY RNAs (sRNAs)

Flashcard 10
Q: What are sRNAs and their size range?
A:

small non-coding RNAs, typically 50–250 nucleotides long.

4. ATTENUATION

Flashcard 17
Q: What happens when tryptophan is scarce?
A:

Ribosome stalls, allowing anti-terminator structure to form → transcription continues.

4. ATTENUATION

Flashcard 16
Q: What happens when tryptophan is abundant?
A:

Leader peptide is translated quickly, forming a terminator hairpin → transcription stops.

4. ATTENUATION

Flashcard 15
Q: What enables attenuation in the trp operon?
A:

Formation of alternative secondary structures in the mRNA leader sequence.

4. ATTENUATION

Flashcard 14
Q: What is attenuation?
A:

A mechanism that causes premature transcription termination based on translation cues.

5. TRANSLATION REGULATION

Flashcard 20
Q: How does RBS accessibility regulate translation?
A:

mRNA structures can block or reveal the Shine-Dalgarno sequence.

5. TRANSLATION REGULATION

Flashcard 19
Q: Example of RNA thermometer usage?
A:

Heat-shock genes activated by melting of 5′ UTR structures.

5. TRANSLATION REGULATION

Flashcard 18
Q: What are RNA thermometers?
A:

mRNA structures that melt at higher temperatures to permit translation.

CONCLUSION

Flashcard 22
Q: What is the benefit of post-transcriptional regulation?
A:

It allows rapid, precise, and energy-efficient gene expression control.

CONCLUSION

Flashcard 21
Q: What are the main mechanisms of post-transcriptional regulation in bacteria?
A:

RNA stability, riboswitches, sRNAs, attenuation, and translational control.

MEMORY AID

Flashcard 23
Q: What mnemonic can help remember post-transcriptional mechanisms?
A:

"R-R-SAT" = RNA stability, Riboswitches, sRNAs, Attenuation, Translation regulation