Eukaryotic Transcription Chapter 26 Flashcards Preview

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Flashcards in Eukaryotic Transcription Chapter 26 Deck (26):
1

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)

2

Which polymerase is Very sensitive to actinomycin D?

RNAP I (RNAP II/III are slightly sensitive)

3

Where are the three RNAPs located?

I - nucleolus II/II Nucleoplasm

4

RNAP I products

Pre-rRNA

5

RNAP II products

pre-mRNA and some snRNAs

6

RNAP III products

tRNA, rRNA, snRNA

7

CTD

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.

8

TFIIH

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

9

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.

10

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

11

TATA box

In Eukaryotes (-31 to -26 region) Conserved region.

12

BRE

In Eukaryotes (-37 to -32 regions) Recognized by TFIIB

13

Pre-initiation complex

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

14

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

15

TAFs

Tata box associated factor

16

TBP

Tata box binding protein; uses b-sheets to interact with DNA, binds minor groove of DNA and bends it, has aromatic AAs,

17

TFIID

Transcription factor, RNAP II, D;

18

TFIIB's role

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

19

TFIIA

Stabilizes PIC complex. primarily TBP with the TATA box.

20

TFIIF

Associated with the RNAP and recruits RNAP to the pre-initiation complex. After TFIIF action, TFIIH and TFIIE are recruited.

21

Mediator complex

20-21 protein complex; interacts with RNAP II and specific transcription factors to change conformation of RNAP II to initiate transcription.

22

TFIIE

needed to aid TFIIH to do its activity.

23

TFIIH

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.

24

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.

25

What is responsible for phosphorylating Ser 2?

P-TEFb which has CDK9 activity.

26

Ser 5 phosphatase

removes phosphate from ser 5 so that polyadenylation factors and termination factors can associate with the tail.

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