Lect 5 Flashcards
(31 cards)
Prokaryotes transcription is catalysed by..
It is complementary to ..and identical to…except
RNA polymerase
Template strand/ anti sense
Coding strand /sense
T and U
Upstream
Downstream
3’
5’
Promoter is
Start point
Numbers are positive
Where RNAP attaches upstrem
+1
Downstream
RNA synthesis phases
Template binding and preinitiation complex
Initiation
Elongation
Termination
Termination seq is
AAU
AAA
Prokaryotic DNA dependent RNA polymerase does not need
Primer
Proofreading
Core RNAP
1w
2a
1b
1b’
Can not recognize promoter
Sigma factor
Recognizes specific promoter
Released after initiation
Holoenzyme
Core enzyme+ sigma factor
Promoter region in 2…..
First is….
Second is….
Consensus seq
-35, 5’ TTGACA 3’»> RNAP binds to it determines transcription freq
-10, 5’ TATAAT 3’»_space; TATA box , pribnow,
TATA box function in prokaryotes
Facilitates the dissociation bet 2 DNA strands due to many A– T bonds making an open complex
Allows RNAP to gain access to transcription site
Ensures fidelity
A consensus seq is
A seq that has the same func in different places in the genome
Preinitiation
Initiation
RNAP holoenzyme and promoter region
Goes to +1 and adds complementary nucleotides by removing pyrophosphate and ester bonds
Elongation
After 10 nucleotides…..is released
How DNA unwinds
….supercoils ahead…behind
Sigma factor
By helicase activity of RNAP
+Ve, -ve
Positive supercoils relaxed by while negative
Gyrase
Topoisomerase 1
During the RNA formation…..forms that is dissociated due to….
DNA-RNA hybrid
DNA rewinding
Termination rho dependent
What is rho
Binds to
It is
Also …dissociated from the strand
A protein that recognizes the termination seq
c- rich strand near the 3’ end of the nascent strand
ATP dependent RNA DNA helicase activity
RNAP
Rho independent termination
Specific DNA seq known as termination site
40-50 bp
Inverted repeats, palindrome
AT rich then CG rich
The transcription of the termination site causes…..due to….
Hairpin loop
Being a palindrome, inverted repeat
Why a string of U’s at the end of termination site
To facilitate unwinding of DNA due to weak attraction of AU
Enzymes and their inhibitors
RNA pol Prokaryotic
Mitochondrial RNAP
Eukaryotic Pol II
Eukaryotic pol III
Strongly rifampicin
Weakly by rifampicin
Strongly by a- amanitin
Weakly by a- amanitin
Eukaryotes transcription have
3 nuclear RNAP and 1 mitochondrial
RNA pol I >45 S RNA (18S, 5.8S,28S)
RNA pol II > mrna, snRNA, miRNA
RNA pol III > tRNA, 5S rRna, 1snRna
Promoter regions in eukaryotes
CAAT box and GC box, -40 to -200 bp, promoter proximal, determine transcription freq
TATA box, hogness box, -20 ,-30 bp
TATAAA
where transcription starts
CAAT box func
CG box func
CAAT box binding transcription factor CTP
Seq specific DNA binding proteins SP1
