Flashcards in Eukaryotic Transcription Chapter 26 Deck (26):
Which RNAP is resistant to a-amanitin (toxin produced by mushroom)?
RNAP I (RNAP II/III 50% inhibition at 0.02ug/mL and 20 ug/mL respectively)
Which polymerase is Very sensitive to actinomycin D?
RNAP I (RNAP II/III are slightly sensitive)
Where are the three RNAPs located?
I - nucleolus II/II Nucleoplasm
RNAP I products
RNAP II products
pre-mRNA and some snRNAs
RNAP III products
tRNA, rRNA, snRNA
Cyan; alternating b-turn subunit; in RNAP II; hydrophillic and phosphorylatable; important for transcription, splicing, termination and capping of RNA (recruit proteins) and RNA processing ; when CTD is not phosphorylated transcription occurs.
Transcription factor needed for RNAP II; includes 5' to 3' and 3' to 5' helicases and is involved in nucleotide excision repair. Has three subunit Cdk7/MO15 + Cyclin H + MAT1 kinase complex that phosphorylates Ser5 of the CTD during transcription initiation
Does RNAP have repair mechanisms?
Yes. 1) Stalls just like DNAP allows polymerase to do reverse reaction to fix (pyrophosphate should be there) 2) polymeration stalls causes RNAP to let RNA fall off and endonucleases peform activity.
Housekeeping genes in Eukaryotes
Typically do not have TATA boxes to initiate transcription. CpG islands, upstream from start site. Methylation of CpG islands can stop transcription
In Eukaryotes (-31 to -26 region) Conserved region.
In Eukaryotes (-37 to -32 regions) Recognized by TFIIB
Platform of transcription factors on promoter sequence to attract RNAP. (TBP-TAFs; TFIID, TFIIB, and TFIIA (platform) TFIIF brings RNAP aids in recruiting TFIIH and TFIIE
Process of RNAPII Attraction
1) TBP + TAFs bind to TATA box 2) TBP-TAFs form TFIID 3) binding of TBP and associated factors causes binding of TFIIB on BRE
Tata box associated factor
Tata box binding protein; uses b-sheets to interact with DNA, binds minor groove of DNA and bends it, has aromatic AAs,
Transcription factor, RNAP II, D;
Binds to BRE and determines the orientation of the RNA polymerase has loop (similar to sigma region 4-3 in prokaryotes) sits in RNAP in eukaryotes
Stabilizes PIC complex. primarily TBP with the TATA box.
Associated with the RNAP and recruits RNAP to the pre-initiation complex. After TFIIF action, TFIIH and TFIIE are recruited.
20-21 protein complex; interacts with RNAP II and specific transcription factors to change conformation of RNAP II to initiate transcription.
needed to aid TFIIH to do its activity.
1) Helicase activity (in both directions, opens up polymerase) 2) TFIIH phosphorylates ser resides, specifically serine 5, on CTD tails of RNAP II causing the recruitment of capping enzymes.
Phosphorylation patterns of CTD
1) CTD must be dephosphorylated to initiate transcription 2) TFIIH (CDK7) with the aid of TFIIE phosphorylates CTD at Ser 5 which aids in capping of RNA 3) TFIIE/H disassociate with CTD, phosphorylates Ser 2 causes recruitment of negative elongation factors (via phosphorylation) and splicing enzymes.
What is responsible for phosphorylating Ser 2?
P-TEFb which has CDK9 activity.