2nd Feb - Transcription VI Flashcards
What are the four key stages of productive transcription?
Recruitment
Initiation
Clearance of the promoter
Elongation
Who won the nobel prize in Chemistry in 2006?
Richard Kornberg for the molecular basis of eukaryotic transcription
Why is RNAP II nicknamed a poor enzyme?
It has few intrinsic functions (unwinding the DNA, RNA synthesis and proof-reading nascent RNA) it relies on auxillary factors for the rest
What are the GTFs required for eukaryotic transcription?
TFIID TFIIB TFIIF TFIIE TFIIH
Describe TFIID
A eukaryotic general transcription factor, that is composed of TBP and 12 TAFs, which bends DNA by about 90 degrees
Describe TFIIB
A eukaryotic general transcription factor which binds the TBP, Pol II and promoter DNA to help fix TSS
Describe TFIIF
Binds the coding strand to keep the transcription bubble open
Describe TFIIE
Recruits TFIIH
Describe TFIIH
Helicase activity unwinds the DNA strands creating the transcription bubble and its kinase activity removes the mediator
What percentage of promoters contain a TATA box?
30%
Is TBP required in TATA less promoters?
Yes it is still required to bind and bend the promoter
What are the core Pol II promoter elements?
BRE - TFIIB recognition element
TATA Box
Initiator (Inr)
Downstream core promoter element (DPE)
What is the role of a transcriptional activator?
To recruit co-activators which modify histones
What is a mediator?
A central control panel in RNAPII transcription which processes and transduces transcriptional regulatory information in all eukaryotes
What is the function of TBPs bending of the promoter?
It wraps the DNA around RNAP II and C-terminal domain of TFIIB placing the TSS in the active site vicinity
What is the eukaryotic pre-initiation complex composed of?
RNA polymerase II and six general transcription factors: TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH.
What is the role of RNAP II’s CTD in promoter clearance?
It contains a heptad repeat YSPTSPS which mediator subunits, elongation factors, 5’ capping and splicing factors use as a docking site.
Mediator subunits promote TFIIH associated CDK-7 phosphorylation of Ser5 –> promoter clearance and mediator dissociation
What is the function of promoter proximal pausing?
Allows 5’ cap addition
Which factors cause promoter proximal pausing?
DSIF and Negative elongation factor (NELF) help stall the polymerase +20 - +40bp downstream of the TSS and the mRNA is capped
What regulates P-TEFb and how?
nc 7SKRNA, it phosphorylates the CTD and NELF and DSIF allowing it to remove NELF and DSIF and recruit Elongin and ELL
What is the function of SETd2?
It binds the CTD and adds H3K6me3 which is recognised by HDAC1
What is FACT?
Facilitates Chromatin transcription helps RNAP get past nucleosomes
