Mod5 - Gene Expression in Eukaryotes

Question 1

Name 3 types of Post-Translational Modification of Histones

Answer 1

Methylation, Acetylation, (Phosphorylation)

Question 2

Once RNA Pol + TFs have bound to the promoter, and SSTFs have bound to the enhancer, which 4 other types of proteins are recruited?

Answer 2

Mediator Proteins, Adaptor Proteins, Histone Acetylase Enzymes, and ATP-Dependent Chromatin Modification Complexes

Question 3

What is the role of Histone Acetylase (HAT)?

Answer 3

Acetylates histones around the site of transcription (which loosens their association with the DNA and allows them to be displaced more easily)

Question 4

What is the role of the adaptor proteins?

Answer 4

Bridge the gaps between the promoter-bound TFs and the SSTFs

Question 5

What is the role of the mediator complex?

Answer 5

MAIN ROLE - moving and displacing chromatin!
(Associates with RNA Polymerase and also helps with activating transcription)

Question 6

What is the role of ATP-Dependent Chromatin Modification Complexes?

Answer 6

Involved in modifying chromatin alongside the mediator complex; recruited by both general TFs and SSTFs.

Question 7

Explain the bipartite nature of SSTFs

Answer 7

They have both a DNA-Binding Domain (a part which recongises a specific DNA sequence) and a Transcription Activation Domain (which recognises the RNA Polymerase and the rest of the basal transcriptional apparatus)

Question 8

How does acetylation affect the function of histones?

Answer 8

Positive lysine group is replaced by negative acetyl group -> therefore, the ‘arms’ of the histone are more negative -> weaker electrostatic attraction to negative DNA so associates less closely -> DNA is more available to be transcribed.

Question 9

Define protein kinases

Answer 9

Proteins which can go on to phosphorylate another protein