26 Questions
What is the primary function of endoribonucleases in mRNA degradation?
To catalyze the internal cleavage of mRNA
Which RNA-binding protein is involved in the processing of ribosomal RNA (rRNA)?
RNase III
What is the consequence of deadenylation on mRNA degradation?
It makes the mRNA more susceptible to exonucleases
What is a factor that influences mRNA stability?
The presence of ribosome-binding sites
Which exoribonuclease is involved in mRNA degradation and can also synthesize RNA in the 3' to 5' direction?
PNPase
What is the direction of mRNA degradation catalyzed by RNase R?
3' to 5'
What is the primary function of the 5' trifosphate group in procaryotic mRNAs?
Protection against 5'-3' exonucleases
What is the consequence of the elimination of pyrophosphate dependent on RppH in the 5' terminal?
Increased susceptibility to endonucleolytic cleavage
What is the direction of mRNA degradation catalyzed by exoribonucleases like RNase II, RNase R, and PNPase?
3' to 5'
What is the role of RNase E in mRNA degradation?
Internal endonucleolytic cleavage
What is the characteristic of the primary transcript produced by procaryotic mRNA synthesis?
A triphosphate group at the 5' end
What is the consequence of the activity of RNase E on the 5' monophosphate group?
Increased susceptibility to exonucleases
What is the direction of the activity of exoribonucleases like RNase II, RNase R, and PNPase?
3' to 5'
What is the role of the 5' trifosphate group in procaryotic mRNAs?
Protection against 5'-3' exonucleases
What is the effect of RppH on the stability of procaryotic mRNAs?
Decreased stability
What is the function of the stem-loop structure at the 3' end of the primary transcript?
Protection against exonucleases
Which process involves the addition of a poly(A) tail and subsequent 3' to 5' degradation of mRNA in E.coli?
Degradation
What is the difference in mRNA degradation between E.coli and B.subtilis?
E.coli uses endonucleases, while B.subtilis uses exonucleases
What is the consequence of failing to degrade aberrant mRNA products?
The cell will accumulate aberrant proteins
What is the role of SmpB-tmRNA in trans-translation?
To facilitate the degradation of aberrant mRNA products
What is the purpose of the poly(A) tail in mRNA degradation?
To mark the mRNA for degradation
What is the difference between the degradation of mRNA in procaryotes and eukaryotes?
Procaryotes use endonucleases, while eukaryotes use exonucleases
What is the consequence of ribosome stalling during translation?
The ribosomes will become stuck and accumulate
What is the function of the 3' exonucleases in mRNA degradation?
To degrade mRNA in the 3' to 5' direction
What is the significance of the 5' triphosphate group in procaryotic mRNA?
It marks the mRNA for degradation
What is the role of the oligoribonuclease in mRNA degradation?
To degrade mRNA exonucleolytically
Study Notes
Prokaryotic mRNA Degradation
Endoribonucleases
- Catalyze the internal cleavage of mRNA
- Create a new 5' end that can be targeted by exoribonucleases
- Examples:
- RNase E: a major endoribonuclease involved in mRNA degradation
- RNase III: involved in the processing of ribosomal RNA (rRNA)
RNA-binding Proteins
- Bind to specific sequences or structures on the mRNA
- Can stabilize or destabilize the mRNA
- Examples:
- Hfq: a protein that binds to small RNAs (sRNAs) and helps regulate their activity
- CsrA: a protein that binds to mRNA and affects its translation and stability
Deadenylation
- The removal of the poly(A) tail from the 3' end of the mRNA
- Can lead to mRNA degradation by making the mRNA more susceptible to exonucleases
- In prokaryotes, deadenylation is not a major mechanism of mRNA degradation, but it can still occur
mRNA Stability
- Influenced by factors such as:
- Secondary structure of the mRNA
- Binding of RNA-binding proteins
- Presence of ribosome-binding sites
- Translation efficiency
- mRNAs with shorter half-lives are often degraded more quickly
Exoribonucleases
- Catalyze the removal of nucleotides from the 5' or 3' end of the mRNA
- Can degrade mRNA in a 5' to 3' or 3' to 5' direction
- Examples:
- RNase R: a 3' to 5' exoribonuclease involved in mRNA degradation
- PNPase: a 3' to 5' exoribonuclease that can also synthesize RNA in the 3' to 5' direction
This quiz covers the mechanisms of mRNA degradation in prokaryotes, including the roles of endoribonucleases, RNA-binding proteins, deadenylation, and exoribonucleases in regulating mRNA stability. It also explores the factors that influence mRNA half-life and degradation. Test your knowledge of prokaryotic mRNA degradation pathways!
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