Transcription LO Flashcards
Describe chemical reaction of RNA pol
- forms phosphodiester bond between 3’ OH and 5’ phosphate of incoming nucleotide.
- OH group nucelophilic attack on phosphoanhydride bond linking alpha and beta phosphates of nucleotide
- results in new phosphodiester bond with 2 inorganic phosphates
what direction does RNA grow in?
3’
what are the 3 steps involved in transcription?
initiation
elongation
termination
what are the 3 parts to initiation?
- RNA pol binds to promoter sequence in dsDNA
- Pol melts dsDNA near transcription start site to form transcription bubble
- pol catalyzes reaction linking first 2 nucloside triphosphates together
what is elongation in transcription?
movement of RNA pol down DNA catalyzing bonds and forming transcription bubble as it moves
What is termination in transcription?
RNA pol releases completed RNA strand and dissociates from DNA
what are the 4 RNA pol?
RNA pol I
RNA pol II
RNA pol III
Mitochondrial pol
what does RNA pol I make?
rRNA (18S, 28S, 58S)
What does RNA pol II make?
mRNA, snRNA,microRNA (regulates gene activity)
What does RNA pol III make?
tRNA, 5S RNA (part of large ribosomal subunit), U6snRNA (involved in spliceosome), 7SK RNA (activates transcription)
what does mitochondrial RNA make in relation to viral pol?
mitochondrial RNA
what is a promoter?
region on DNA where transcription factors bind that are involved in transcription initiation
What is the sequence of the TATA box?
5’ TATAAA 3’
where is the TATA box located?
30 bp upstream of transcription initiation site
what is the function of the TATA box?
determines transcription start site and directs binding on RNA pol II
how does alpha-amanitin block transcription?
non-competitive inhibitor, binds allosterically to bridge helix (alpha helix between upper and lower jaws of RNA pol), blocks RNA chain elongation by preventing translocation of RNA
how does rifampicin block transcription?
binds to beta subunit of bacterial RNA polymerase selectively. Blocks the RNA exit channel thus preventing elongation of mRNA
what is Rifampicin used to treat?
broad spectrum for tuberculosis and leprosy
what is the function of XPD and XPB?
DNA helicases used in transcription within TFIIH complex
what is the function of CDK7?
kinase that phosphorylates C-terminal domain of RNA pol II which allows it to release from promoter
what is the function of TFIIA?
stabilized binding of TATA box binding protein (TBP) to DNA
Does not specifically recognize DNA
what is the function of TFIIB?
bridge between TFIID and RNA pol II
what is the function of TFIID?
initially recognizes the promoter
what is the function of TFIIE?
involved in DNA melting at the promoter
what is the function of TFIIF?
assists in wrapping DNA around the pre-initiation complex (PIC)
what is the pre-initiation complex (PIC)?
a group of general transcription factors that help bind RNA pol to the promoter and melt DNA
what diseases do mutations in XPB, XPD, and p44 cause?
xeroderma pigmentosum, cockaynes syndrome, and trichothiodystrophy
