FoM:L6 - Regulation of gene expression

Question 2

What is spatial and temporal control of protein expression?

Answer 2

• spatial: different cells produce different proteins
• temporal: different cells express different levels of a protein at any one time

Question 3

What is transcriptional control of protein production?

Answer 3

impacts transcription, 4 main levels:
- binding of RNA polymerase
- long-range control
- chromatin remodelling
- methylation

Question 4

What are transcription factors?

Answer 4

• control gene expression
• bind to DNA in major groove of double helix
• bind to a DNA binding motif
• repressors or activators

Question 5

How are genes expressed by activators?

Answer 5

• bind to promoter
• interact with RNA polymerase
• in bacteria: involves interaction with metabolite

Question 6

How are genes controlled in eukaryotes?

Answer 6

• general TFs bind to TAATA box
• different combinations of regulatory proteins (different for different genes)
• DNA looping facilitates interaction

Question 7

How can regulation occur over long distances?

Answer 7

• Locus control regions (linked to genes)
• chromatin remodelling

Question 8

What may control the activity of regulatory proteins?

Answer 8

• protein synthesis
• covalent modification
• ligand binding
• inhibitors binding
• unmasking

Question 9

How can TFs be activated by ligands?

Answer 9

• ligands change conformation or shape of TF
• ligands bind to GPCRs and stimulate intracellular pathway resulting in TF activation
• cytokines binding to receptors cause degradation of inhibitor protein and activation

Question 10

What is chromatin remodelling?

Answer 10

• unwinding of DNA in response to activators
• acetylation pattern of histones can allow activating proteins to bind

Question 11

What are HATs and HDACs?

Answer 11

HATs: histone acetyltransferases (increase gene expression)
HDACs: histone deacetylases (reduce gene expression)

Question 12

What is the effect of acetylation on gene transcription?

Answer 12

• increased acetylation
• less tightly wrapped
• more accessible

Question 13

What happens to the X chromosome in females?

Answer 13

• 1 becomes deactivated/inactive
• highly condensed
• XIST gene transcript

Question 14

What is methylation?

Answer 14

• methylation at C residues (CpG sites)
• turn off gene expressions
• heritable

Question 15

How can gene expression be modified post-translation?

Answer 15

• mRNA processing (alternative splicing)
• mRNA export (nuclear export controlled)
• mRNA localisation (directed to specific areas)
• negative translational control
• regulation of mRNA stability (ore immediate)

Question 16

What targets proteins for degradation?

Answer 16

• proteasome (large protein complexes, proteolysis)
• ubiquitin conjugation (by ubiquitin ligases)

Question 17

List all the ways/times where protein production can be controlled

Answer 17

1) transcriptional control
2) RNA processing control
3) RNA transport and localisation
4) Translation control
5) mRNA degradation
6) protein activity control