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CMB2001 > L9-10: Post transcriptional control of gene expression II > Flashcards

L9-10: Post transcriptional control of gene expression II Flashcards

1
Q

ribosome

components?

A

natural ribozyme doing more than phosphoidester bond shuffling

1/3 protein
2/3 RNA

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2
Q

pro vs euk ribosomes

A

euk> 80S (30S and 50S)
pro> 70S (40S and 60S)

eukaryotic ribosomes are more complex

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3
Q

components of tRNA

A

TC loop
variable loop
anticodon
anticodon loop
D loop

in P/A sites / delivers aa

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4
Q

charging of tRNA

catalysis?

A
  1. aa activation> aa/ ATP bind catalytic site
  2. nucleophilic attack by alpha carboxylic acid aminoacyl adenylate (aa-AMP)
  3. hydroxyl group of adenine 76 of tRNA attacks carbonyl carbon of adenylate&raquo_space; aminoacyl-tRNA / AMP

catalyzed by amioacyl-tRNA synthetases

peptide bond formation catalyzed by ribozome

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5
Q

translation catalysis

A

by RNA

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6
Q

translation elongation

driver?

A

Aminoacylated tRNA binding site A
ribosome moves along 3 bases to bring next codo into A site
moves into polypeptide chain site P where expanding polypeptide chain is attached

elongation factor G drives

RNA-catalysed event

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7
Q

elongation factor G in eukaryotes

A

eEF2
drives translational elongation

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8
Q

peptide bond formation

A

catalysed by ribosome

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9
Q

eukaryotic translation initiation

A

small sub-unit binds CAP
scans AUG to start
initiating methionine

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10
Q

kozak consensus sequence

A

most frequently found around AUG

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11
Q

mRNA circularization requirements

Elf4F complex

A

elF4E (G cap binding)
Elf4A (ATPase/ RNA helicase)
Elf4G (binds ElF4E/A/3/PAB)

requires elF4E/ G / PAB

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12
Q

mRNA circularisation function

A

monitors mRNA integrity
moves ribosomes ending translation close
key tln factors

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13
Q

Elf1A

A

80S dissociation/ met-tRNA binding to 40S

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14
Q

Elf!

A

AUG recognition

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15
Q
A
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16
Q

ElF5

A

stiumlates ElF2 GTPase
GAP for Elf2

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17
Q

Elf3

components/ function

A

mutlifactorial complex of ElF1A/ElF1/ElF5
prevents 60S binding

18
Q

ternary complex

A

Met tRNA in complex w initiation fcator/ ElF2 and GTP

19
Q

ElF2

A

binds ElF 5
met-tRNA binding
GTPase

needs to be recycled for ternary complex generation > further initiation

20
Q

48S PIC

A

small sub-unit primed for mRNA association

binds to ElF4G w ElF4E/4A

21
Q

43S association requirements

A
  1. ElF3/4G interaction
  2. RNA unwinding > ElF4F (4A)
22
Q

which elf binds cap

A

ElF4A
also works w PAB to circularize

23
Q

translocation in eukaryotic translation

A

required for mRNA/tRNA movement through ribosome

24
Q

when does translation regulation occur?

A

initiation

25
Q

translation regulation stages

A
  1. ElF4F binding on mRNA
  2. 43S binding
  3. ElF2B/ ternary complex formation
    - drives ElF2 cycle/ regulation
26
Q

ElF2 cycle/ regulation

A
  • ElF2 leaves small sub-unit
27
Q

Iron response elements
IRE

A

hairpin loops w conserved loop sequence and bulge in stem
5’/3” UTRs of Fe-regulated RNAs
bound by Fe regulatory proteins IRP1/2

28
Q

IRPs in low Fe

A

IRPs 1/2 bind to IRE of 5’ UTR
decreases expression of proteins in storage
“ bind 3’ UTR
stabilise RNAs as targets for ribonucleases
mRNA stabilized

29
Q

IRPs in high Fe

A

IRP1/2 deactivated
- 2 degraded
- 1 binds to FeS clusters / prevents IRE binding > RNA release

translation of target proteins

transport protein mRNA degradation

30
Q

IRP1

A

bifunctional protein
binds FeS clusters in high iron
> no RNA binding / becomes c-aconitase

31
Q

c-aconitase

A

interconverts citrate and isocitrate

32
Q

ElF2b

A

controls active ElF2-GTP levels/ initiation rate
decreases w stresses
ElF2 phosphorylation regulates/ comp inhibits ElF2b> ternary complex impairment/ decrease in mRNA initiation

lower level than ElF2

33
Q

ElF2 sub-units

A

alpha/ beta/ gamma
alpha> phosp on ser51 by PKRI/PERK/GCN2/HRI
Beta> binds 2b/5
gamma GTPase/ met-tRNA kinase

34
Q

ElF2 kinases

A

PKR
PERK
GCN2
HRI

dimerize under stimulatory conditions/ autophosphorylate and act on subs

35
Q

PKR activation

A

by dsRNA
viral infection

36
Q

PERK

A

Mediator of unfolded protein response/ ER stress

37
Q

GCN2

A

regulator of tln in response to aa availability

38
Q

HRI

A

links globin availability to protein synthesis

39
Q

2 PKR domains

A

regulatory
kinase

40
Q

PKR expression

A

low expression normally
increases w interferon exposure

viruses release

41
Q

iron metabolism regulation

A

Fe levels regulate iron storage/ transport protein expression

haem/ FeS clusters for redox/ gene exp

42
Q

UTR

A

untranslated region
5’/3’ can influence translation

CMB2001 (4 decks)

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