4-4: Post-Transcriptional Regulation

Question 1

What is transcriptional attenuation?

Answer 1

Regulation involving prematurely terminating mRNA synthesis

Question 2

How do you regulate transcription at the RNA level

Answer 2

Attenuation, control mRNA stability (how long before degradation), translation efficiency

Question 3

How is translation efficiency controlled?

Answer 3

By controlling whether or not RBS is free to be bound to the ribosome

Question 4

What is RNA regulation controlled by?

Answer 4

RNA regulatory elements

Question 5

What terminator leads to transcriptional attenuation

Answer 5

Rho-independent (intrinsic)

Question 6

How long do bacterial transcripts last?

Answer 6

Half life is from seconds to an hour.

Question 7

What are ribonucleases?

Answer 7

enzyme degrades mRNAs, found in all cells

Question 8

What is needed for translation to initiate?

Answer 8

The RBS of the gene needs to be free (cannot be base paired to rRNA in the ribosome)

Question 9

What are two ways that stem loop structures can shut off gene expression?

Answer 9

1. Involve the RBS
2. Involving the formation of a transcriptional terminator upstream of the gene

Question 10

Function of sRNA

Answer 10

Regulate gene expression

Question 11

How do sRNA work

Answer 11

Base-pair to mRNA which affects RBS availability or attracts ribonuclease

Question 12

How complimentary are sRNAs?

Answer 12

Very limited - only about 5-11 nt

Question 13

What is Hfq

Answer 13

RNA chaperone that helps sRNA bind to mRNA complementary sequence (binds both to stable their interaction)

Question 14

What are riboswitches

Answer 14

Ligand-binding RNAs - adopt intricate 3D structures that bind a specific molecule
Binding helps them sense their environment

Question 15

Where are riboswitches located

Answer 15

5’UTR of bacterial mRNAs - regulate expresion of downstream genes on the SAME RNA

Question 16

What happens upon ligand binding to riboswitches?

Answer 16

It will change RNA structure in the 5’ UTR, thus inducing or repressing downstream genes

Question 17

In what domains are riboswitches found in?

Answer 17

All three, but they are mostly characterized in bacteria

Question 18

How do riboswitches work

Answer 18

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

Question 19

Forms of post-translation regulation

Answer 19

Feedback inhibition, protein-protein interaction, post-translational modification

Question 20

What do proteases do

Answer 20

Clear away/recycle misfolded proteins, or specific proteins
Some proteins need proteases to cleave linkage to be activated