When is TBP alone able to recruit RNAP to initiate transcription?
When a particular promoter contains only the TATA box
In a TATA-less promoter with Inr and DPE, TBP can still bind to the promoter
T/F
False
What happens with TBP when there is a TATA-less promoter with a GC box in the proximal promoter?
In a TATA-less promoter with a GC box in the proximal promoter, TBP cannot bind by itself to initiate transcription
How can TFIID bind to a TATA-less promotor?
via the interaction with the GC-box, bound with Sp1
What do TAFs do when associated with DNA?
(tata-associated factors)
TAFs not only interact with DNA to anchor TFIID to the promoters
also bring activator proteins (bound elsewhere in the gene) to the promoter complex
What activities does TAF1 have?
Histone acetyltransferase (HAT) attaches acetyl groups to lysines on histones (enhances transcription)
Protein kinase phosphorylates TAF1, TFIIF/A/E to aid in assembly of the pre-initiation compelx
What does TFIIA bind to and what is its major function?
TFIIA binds to TBP and its major function is to stabilize binding between TFIID and promoter, thus promoting formation of the DA complex on the DNA
What does TFIIB bind to and what occurs with this interaction?
its interaction with TBP and DNA is thought to “orient” the complex on the promoter marking the direction of future transcription and selecting the strand to be transcribed
TFIIB stabilizes TBP-TATA box binding and interacts with transcription activators that bind to upstream elements
What GTF is required for RNAPII to also join the pre-initiation complex?
TFIIB
(RNAP will bind to the DAB complex, but not to the DA complex)
Describe how the N and C terminals of TFIIB interact in the preinitiation complex:
the N-terminal domain of TFIIB interacts with RNAPII
C-terminal domain interacts with TBP
Which RNAPII factor has some similarities to the prokaryotic sigma factor?
RAP30 protein (RNA assocaited protein) of TFIIF
it mediates binding of TFIIF to the RNAPII core
What is thought to be the purpose of the two subunits of TFIIE?
TFIIE consists of two subunits, TFIIEa and b, and is thought to be involved in DNA melting at the promoter
TFIIE function is essential both for transcription initiation and for promoter clearance
Which general transcription factor is essential for both transcription and NER?
TFIIH
Which transcription factors are required to clear the promoter but leave during transcriptional elongation?
TFIIE and TFIIH
Which transcription factor tracks alone with RNAPII during elongation?
TFIIF
What do long range promoter elements require to convey activation to RNAPII?
Many activators that are bound to enhancers and other long-range promoter elements require the function of the Mediator complex to convey the activation signal to RNAPII
What does the mediator complex do?
The Mediator complex transduces both positive and negative regulatory information to RNAPII by physically bridging distantly located transcription factors with RNAPII
When is a mediator complex required?
It transduces both positive and negative regulatory information to RNAPII
It is only required for transcriptional initiation and not elongation
What construct at the promoter can facilitate additional rounds of transcription?
Scaffold complex
Once initial assembly of the PIC is completed and the initial round of transcription has started, additional rounds of transcription may be facilitated by a Scaffold complex that would remain at the promoter, thereby speeding up assembly of a new PIC
What is the scaffold complex composed of?
TFIIA/E/D/H and Mediator
Subsequent re-initation only requires recruitment of RNAPII, TFIIF, TFIIB
