4-Transcription Flashcards
How many RNAP types do bacteria have?
1
How many RNAP types do eukaryotes have?
3
How many RNAP types do Archaea have?
1
Whats is the Archaea RNAP similar to? Do they have similar TFs?
Eukaryote RNAP2, Yes have similar protein to TATABP that is in TF D
what is an apoenzyme?
enzyme that requires cofactor but that does not have one bind
What is a Holoenzyme?
apoenzyme and it’s cofactor e.g RNAP complex (it is complete and catalytically active and coenzymes are usually tightly not covalently bound with the exception of Iron ions/vitamins)
Where does RNAP bind to?
promoter
what is needed to enable transcription initiation?
Activation of RNAP
What does elongation lead to?
clearing of the promoter which enables the transcription process to begin again
What two levels can transcription be regulated by?
a) the promoter level (cis regulation) b) the polymerase level (trans regulation) note:these elements vary in bacteria and eukaryotes
what is needed for bacterial transcription termination?
P factor
what are B’B’ subunits in bacterial RNAP involved in?
CLAMP (These residues are mobile domains that are part of the “crab claw” structure that swing open and closed, effectively changing the size of the active site channel. )
what is w subunit in bacterial RNAP involved in?
stabilising the RNAP
what is B subunit in RNAP in bacteria involved in?
B flap traps mRNA
what subunits form active site in bacterial RNAP?
BB’
what does alpha subunit in RNAP in bacteria do?
binds DNA
What does the rudder in RNAP in bacteria do?
destabilises RNA/DNA hybrid
what are the two main sigma factors in RNAP in bacteria?
sigma 70 for general purpose and sigma S for stationary phase
what are the 3 types of Eukaryote RNAP and what do they transcribe?
RNAP1-rRNA RNAP2-mRNA RNAP3-tRNA
what type of RNAs are highly and moderately sensitive to alpha amanitin (an amatoxin)
(it is an Inhibitor) RNA polymerase I is insensitive, RNA polymerase II is highly sensitive, RNA polymerase III is moderately sensitive
Upon ingestion and uptake by liver cells what does alpha amanitin do?
it binds to the RNA polymerase II enzyme, effectively causing cytolysis of hepatocytes (liver cells)
How is eukaryotic RNAP different to bacterial RNAP? (2)
no sigma unit and possesses c-terminal doman tail (CTD)
what does bacterial RNAP require for initiation?
sigma factor
what does eukaryotic RNAP need for initiation?
increase in TFs and several promoters
what are the 3 main TFs?
TF2B,TF2D,TF2H
what is main component of TF2D?
TATA Binding protein
what does TF2D show some homology to?
sigma factor
what does BRE stand for?
TF2B response element
role of TF2H (2)
melts DNA and phosphorylates CTD
role of TF2D
recognise TATA box
role of TF2B (2)
recognise BRE and positions RNAP2
why is elongation in eukaryotes harder?
many nucleosomes (need to alter histones)
How do you loosen histone binding?
1)histone acetyltransferase adds ch3coo to lysines
what is polyadenylation?
the addition of a poly(A) tail to a messenger RNA. The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases
when does process of polyadenylation begin?
begins as the transcription of a gene finishes, or terminates
what is poly(A) tail important for? What happens to the tail over time?
Nuclear export, translation, and stability of mRNA. The tail is shortened over time, and, when it is short enough, the mRNA is enzymatically degraded
what are bacterial RNAP subunits?
B’B’,B’B,B,w,2*a,rudder
How many RNAP subunits?
6
