4-4: Post-Transcriptional Regulation Flashcards
What is transcriptional attenuation?
Regulation involving prematurely terminating mRNA synthesis
How do you regulate transcription at the RNA level
Attenuation, control mRNA stability (how long before degradation), translation efficiency
How is translation efficiency controlled?
By controlling whether or not RBS is free to be bound to the ribosome
What is RNA regulation controlled by?
RNA regulatory elements
What terminator leads to transcriptional attenuation
Rho-independent (intrinsic)
How long do bacterial transcripts last?
Half life is from seconds to an hour.
What are ribonucleases?
enzyme degrades mRNAs, found in all cells
What is needed for translation to initiate?
The RBS of the gene needs to be free (cannot be base paired to rRNA in the ribosome)
What are two ways that stem loop structures can shut off gene expression?
- Involve the RBS
- Involving the formation of a transcriptional terminator upstream of the gene
Function of sRNA
Regulate gene expression
How do sRNA work
Base-pair to mRNA which affects RBS availability or attracts ribonuclease
How complimentary are sRNAs?
Very limited - only about 5-11 nt
What is Hfq
RNA chaperone that helps sRNA bind to mRNA complementary sequence (binds both to stable their interaction)
What are riboswitches
Ligand-binding RNAs - adopt intricate 3D structures that bind a specific molecule
Binding helps them sense their environment
Where are riboswitches located
5’UTR of bacterial mRNAs - regulate expresion of downstream genes on the SAME RNA
What happens upon ligand binding to riboswitches?
It will change RNA structure in the 5’ UTR, thus inducing or repressing downstream genes
In what domains are riboswitches found in?
All three, but they are mostly characterized in bacteria
How do riboswitches work
RNA domain called an aptamer binds ligand which changes base pairing in 5’UTR of mRNA and forms either:
1) A stem-loop that sequesters RBS
or
2) transcriptional terminator that prevents gene transcription
Forms of post-translation regulation
Feedback inhibition, protein-protein interaction, post-translational modification
What do proteases do
Clear away/recycle misfolded proteins, or specific proteins
Some proteins need proteases to cleave linkage to be activated
