Eukaryotic Transcription 5 Flashcards
1
Q
SRBs
A
- bind to the CTD of RNA pol II large subunit in yeast
- suppressor of RNA pol B
2
Q
Mutation of SRB4: how severe?
A
mutations in these genes overcome mutations in the CTD, which implies that SRBs interact with the CTD
- a mutation in SRB4 eliminates 93% of transcription in both basal and activated
3
Q
SRB4: which module?
A
head of the mediator
4
Q
Sin4 deletion: tail-less mutant; consequence
A
are defective in activated transcription
5
Q
what is the role of Cdk8/CycC in inhibiting action of TFIIH?
A
- Srb10/Srb22 module inhibits TFIIH by phosphorylating the cycH subunit of H
- the cdk8 module is dissociable
6
Q
what are the two ways to build affinity column to capture Mediator
A
- can be purified using an affinity column with immobilized CTD
- can also purify using VP16 acidic activator column
7
Q
Model for how Mediator modulates amplitude of transcription
A
- Transactivators determine the Mediator conformation, which in turn, controls the rate of RNA polymerase entry onto the promoter. Thus Mediator controls the rates of initiation and reinitiation.
- Specific Mediator conformation determined by transactivator contact.
8
Q
What controls Mediator conformation?
A
x
9
Q
mediator
A
- large complex of proteins known as the mediator is also apart of the preinitiation complex
- contains 24 subunits
- purify with RNA pol 2 and binds to CTD
10
Q
Mediator complex activities
A
- 5 - 10 fild increase in basal transcription
- 30 - 50 fold stimulation of TFIIH dependent phosphorylation of the CTD
- integrator of positive and negative signals
11
Q
head of the mediator complex
A
- attachment sites to RNA pol 2 and the CTD of RNA pol 2
- Srb4
12
Q
middle of the mediator
A
- Med9/10
- specific function unclear
13
Q
Tail of mediator
A
- Gal 11 module
- contacts with transactivators and repressor proteins
- Sin 4 mutants
14
Q
Rbp4/7
A
- mediator contacts Rbp4/7 subunits and triggers the opening of the clamp
- this provides better access for DNA to enter the active site of the polymerase
15
Q
SWI/SNF proteins
A
- disrupts nucleosome structure resulting in 30 fold increase in binding of transactivator proteins
