Eukaryotic Gene expression Flashcards

1
Q

what is control used for in euk gene expression?

A

regulate the genetic program that underlies embryonic development and tissue differentiation; gene expression patterns must remain permanent, even for decades–>activating signals may be transient

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2
Q

what ar ethe RNA pols in a euk?

A

Pol I, Pol II, and Pol III

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3
Q

what is the role of Pol II?

A

similar to bacterial RNA pol; transcribes the majority of protein coding genes and microRNAs

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4
Q

what is the role of pol I?

A

transcribes for larger ribosomals RNA

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5
Q

what is the role of pol III?

A

transcribes short RNAs such as 5S rRNAs and tRNAs

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6
Q

each euk pol has more than just single sigma TF–alows for much more intricate gene control and need to displace chromatin

A

ya

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7
Q

7 additional subunits attach to RNA pol II

A

ya

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8
Q

what is the purpose of TFIID?

A

various subunits of it recognize the TATA, INR (initiator) and DPE (downstream promoter element) seq domains

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9
Q

what composes TFIID?

A

12 subunits (human), including the TBP (TATA binding protein)

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10
Q

what is the point of TBP?

A

to bind TATA in the minor groove at the con seq TATA(A/T)A(A/T)

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11
Q

what is the purpose of BRE?

A

a sequence upstream of the TATA box for which TFIIB binds to

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12
Q

what is TFIIB?

A

basal factor; binds BRE; binds both TFII-D and pol–>brings pol to promoter; gives polarity since the TATA box is symmetrical

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13
Q

what is the purpose of TFIIA?

A

stabilizes the binding of TFIIB

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14
Q

what is the purpose of TFIIF?

A

stabilizes the binding between TFIIB and RNA pol II

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15
Q

genes aren’t in a total on/off state, but the rate of transcription can be increased or decreased

A

ya

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16
Q

what is the purpose of the mediator complex?

A

integrates signals of whether a gene needs to be up- or down-regulated; it brings the Pol II complex to wherever it’s needed–>these signals increase or decrease; allows for long-range control (through bending of DNA); can also integrate multiple signals by binding to many different places on DNA–>the different signals may increase transcription by 20%, others may inhibit by 40%, etc

17
Q

TFIIS role

A

elongation factorl; keeps pol II from stalling, has proofreading activity, stimulates hydrolysis of incorrect rNTPs

18
Q

purpose of introns?

A

allows for multiple RNA forms to arise from one gene

19
Q

we can possible judge organism complexity based on number of introns

20
Q

what is the role of GT/MT?

A

guanylyn transferase/methyl transferase; needed for capping

21
Q

What is the purpose of TFIIH?

A

helicase (requires TP) /kinase–phosphorylate other proteins in the complex; required for expression of some genes–creates the bubble to allow RNA synth

22
Q

what is the role of P-tef-B

A

modifies Pol II tail to release the initiation complex; (involved in elongation)

23
Q

what is the role of CstF and CPSF?

A

cut 35 bases after AAUAAA

24
Q

what does PAP do?

A

add the poly-A tail

25
what is the purpose of PAB?
acts a ruler and binds As to set the length of the tail
26
what is the purpose of TFIIE?
recruits TFIIH
27
what is the heptad con seq in the C term domain of pol II?
Tyr-Ser-Pro-Thr-Ser-Pro-Ser; ser5 phos. RNA pol 2 for activation by a subunit of TFIIH; pTEFb transitionsRNA ol phos to ser2 (and dephos of ser 5 by phosphatases) as it moves through the gene
28
why is RNA capping used, and what happens?
to improve stability of mRNA, as exonuclease has a substrate specificity for 5' ends of RNA/DNAs Step 1: 5'5' bond between 5' end of mRNA and guanine is catalyzed by guanylyl transferase Step 2: Guanine cap is methylated by guanine-7-methyl transferase
29
most plants and animals can also methylate the 2' carbon of deoxyribose of the +1 nuc and vertebrates can methylate 2' of 2+ nt
ya
30
what creates the polyA tail?
cleavage stimulation factor (CstF) and CPSF (cleavage and polyadenylation specificity factor); PAP then works much more quickly when CstF and CPSF o their job--can add up to 250 As
31
what signals may termination utilize?
2 signals: 1. Lack of CstF and CPSF attached to pol II tail (CTD tail)--antitermination factors--and possibly promoting other binding factors to leave (termination factors) 2. 5' end of the cleaves mRNA now has no cap--5'3' mRNA exonuclease (Xnr2)