Control of Gene Expression

Question 1

What are the six aspects of Control of Gene Expression?

Answer 1

1. Chromatin-level Control
2. Transcriptional Control
3. Post-Transcriptional Control
4. Translational Control
5. Post-Translational Control
6. Gene Amplification

Question 2

What does Chromatin-level Control encompass?

Answer 2

1. Histone Modification

2. DNA Methylation

Question 3

How does the structure of a histone molecule allow for histone modification?

Answer 3

The N-terminus of a histone molecule in a nucleosome protrudes outward from the nucleosome. These histone tails are accessible to various modifying enzymes, which catalyse the addition or removal of specific chemical groups.

Question 4

What happens during Histone Acetylation?

Answer 4

1. Acetyl groups are attached to lysines in histone tails, catalysed by histone acetyltransferase.
2. When lysines are acetylated, their positive charges are neutralised and histone tails no longer interact with the neighbouring nucleosomes.
3. Electrostatic interaction between neighbouring nucleosomes promotes folding of chromatin into more compact structure.
4. When this interaction does not occur in an acetylated region,
   - Chromatin has a more diffused structure
   - Transcription factors have easier access to genes

Question 5

Role of Histone Acetylation

Answer 5

1. Promote transcription initiation by remodelling the chromatin structure
2. Histone acetyltransferase binds to and aids in the recuitment of the transcription machinery