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3382 > Eukaryotic Gene Expression and Regulation > Flashcards

Eukaryotic Gene Expression and Regulation Flashcards

1
Q

How does structure of genome and RNA Pol compare between prokaryotes and eukaryotes?

A

prok: single, circular, with plasmid, small; 1 RNA Pol
euk: chromosomes in nucleosome large; 3 RNA Pol

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2
Q

How does transcription and translation compare between prokaryotes and eukaryotes?

A

prok: coupled bc no nucleoid barrier, default is ON for transcription
euk: nuclear transcription and cytoplasmic translation; default is OFF for transcription

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3
Q

How does gene clustering compare between prokaryotes and eukaryotes?

A

prok: operons where genes with similar functions are grouped
euk: usually no operons; each gene has its own promoter and enhancer elements

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4
Q

How does DNA structure compare between prokaryotes and eukaryotes?

A

prok: highly supercoiled DNA with some associated proteins
euk: highly supercoiled chromatic associated with histones in nucleosomes

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5
Q

Why is the default for euk transcription off?

A

genes not frequently expressed are “inactive” region of chromatin, which is packaged to be inaccessible to regulatory factors

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6
Q

What is the rate limiting step of transcription?

A

difference in rate of initiation (tells abundance of specific mRNA)

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7
Q

all genes require — to recruit RNA Pol to promoters

A

general transcription factors (GTFs)

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8
Q

What is the location and role of RNA Polymerase I?

A
  • located in nucleolus
  • transcribes most rRNA
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9
Q

What is the location and role of RNA Polymerase II?

A
  • located in nucleus
  • transcribes most protein-encoding genes (mRNA)
  • also does snRNA (for splicing) and miRNA
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10
Q

What is the location and role of RNA Polymerase I?

A
  • located in nucleus
  • transcribes other RNAs like 5S rRNA, tRNA, and snRNA
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11
Q

What does alpha-amanitin do?

A

inhibitor that RNAPII shows the most sensitivity to

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12
Q

What are the activities of RNAP?

A
  • **sequence specific **DNA binding (promoter)
  • melts DNA to reveal the template strand
  • selects ribonucleotide (not deoxynucleotides) that anneals to template strand
  • polymerizes RNA strand
  • translocates on DNA template, during which it must:
    -unwind DNA in front of polymerase
    -unwinds RNA:DNA hybrid
    -rewinds DNA behind polymerase
  • recognize termination signals in the nascent transcript (or on the DNA template)
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13
Q

RNAP must be what quality?

A

processive (have a high probability of reaching the end of the gene)

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14
Q

What are the E. coli core RNAP subunits?

A

B’, B, αI, αII, ω

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15
Q

How do the three eukaryotic RNAPs compare to E.coli RNAP and each other?

A
  • all 3 RNAPs have all** 5 E.coli- like subunits + 4 other common subunits**
    -** RNAP I and III** have the same 2, non-identical α-like subunits
  • RNAP II has a C-terminal domain that needs phosphorylation
  • all have **3-7 smaller subunits **for promoter class recognition
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16
Q

What is the importance of the CTD of RNAPII?

A
  • seq: YSPTSPS
  • 5/7 residues are hydrophilic
  • ## phosphorylation at S and T
17
Q

What happens when increased vs. decreased phosphorylation of CTD of RNAPII?

A
  • low CTP (hypo)phosphorylation = transcription initiation
  • high CTD (hyper)phosphorylation = elongation
18
Q

What are the 3 steps of transcription?

A
  1. initiation
  2. elongation
  3. termination
19
Q

How does eukaryotic initiation by RNAPII occur?

A
  1. 5 GTFs associate with TATA box in the promoter
  2. RNAPII attaches to GTFs and initiation region in promoter making a loop
  3. transcription activators/repressors bind to enhancer/silencer regions that are proximal or distal to promoter
20
Q

How does eukaryotic elongation by RNAPII occur?

A
  1. RNAPII released front initiation complex
  2. emerging RNA gets 5’ cap
  3. decide if gene should be aborted or not
21
Q

How does eukaryotic termination occur?

A
  • there are no termination sequences defined
  1. torpedo model
  2. allosteric model
22
Q

what is the torpedo model

A
  • mRNA cleaved after polyA signal sequence
  • RNase digests remaining RNA and disrupts transcription complex

potential eukaryotic termination model

23
Q

what is the allosteric model?

A
  • polyA sequence causes change in RNAPII processivity
  • causes RNAPII to dissociate

potential eukaryotic termination model

24
Q

How is prokaryotic transcription different from eukaryotic transcription?

A
  • initiation doesn’t need TFs
  • RNAP can bind directly to DNA
  • in cytoplasm
  • no rRNA processing
25
Q

How is eukaryotic transcription different from prokaryotic transcription?

A
  • need 5 GTFs for initiation
  • RNAP is not DNA binding
  • transcribes pre-mRNA
  • in nucleus
  • RNAP has more subunits
  • no discrete termination signal
26
Q

How is prokaryotic transcription similar from eukaryotic transcription?

A
  • same 3 steps
  • RNAP recognizes promoter
  • 5’ to 3’
  • DNA template to make RNA

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