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BMS > Translation (Copeland) > Flashcards

Translation (Copeland) Flashcards

1
Q

3’ UTR is site of

A

Key regulatory sequences

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2
Q

Stop codons

A

UGA, UAA, UAG

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3
Q

5; 7-methyl GMP cap is site of binding of

A

initiation factors

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4
Q

3’ CCA end of tRNA is not ___

A

Transcribed! It is added after processing

-need CCA end of enzyme can teach

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5
Q

Aminoacylation requires

A

ATP

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6
Q

Amino acyl tRNA synthetase

A

Recognizes tRNAs and adds appropriate amino acid

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7
Q

If incorrect amino acid is in the CCA 3’ site (synthesis site) it is moved to the

A

Editing site and removed

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8
Q

Eukaryotic ribosome properties

A

80S (60S + 40S)
-mostly RNA –> Ribozyme

-3 tRNA binding sites

5’ E P A 3’

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9
Q

Initiation and elongation occur

A

Simultaneously

-yield multiple ribosomes on single mRNA molecule –> V large complex “polysomes”

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10
Q

What is the most important for regulation of translation?

A

Initiation

  • assembly of ribosome & mRNA
  • positioning of ribosome on start codon
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11
Q

EIF2

A

Eukaryotic transcription factor

Binds & delivers initiator Met-tRNA

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12
Q

EIF4E

A

Binds 5’ cap

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13
Q

EIF4G

A

Scaffold protein, binds eIF4Erequired for assembly of pre-inc complex

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14
Q

What causes eIF2 release so 60S subunit can bind?

A

GTP hydrolysis

  • only step that requires ATP
  • once AUG found, eIF2 dissociates, eIF4E, eIF4G dissociate (stay at 5’ cap), ribosomal subunit binds
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15
Q

What is the movement of ribosome down mRNA and amino acid tRNA delivery called

A

Elongation

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16
Q

What is eEF1A

A

Binds all tRNAs except initiator and selenocysteine

  • GTP bound to it
  • delivery of aa-tRNA
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17
Q

How does eEF1A get released

A

GTP hydrolysis

-incorrectly base-paired tRNAs disassociates

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18
Q

What is eEF2

A

Catalyze so translocation; pushes from Asite to P site

  • ribosome translocation
  • proofreading in ribosomal A site codon/anticodon pair checked by ribosome conformation
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19
Q

What causes eEF2 release

A

GTP hydrolysis

-completion, A space is open for business

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20
Q

What is eRF1

A

Protein involved in termination

  • swoops in and allows for peptide hydrolysis and termination
  • recognizes any of the top codons
  • there is no terminator tRNA; eRF1 catalyze a release of completed peptide
21
Q

What dictates initiation in bacterial translation

A

Shine-dalgarno sequence

22
Q

Is 5’ cap required in bacteria

A

No

Also transcription and translation is coupled

23
Q

Describe bacterial ribosome

A

-smaller
70S ribosome (30S + 50S)
-allows for selective inhibition by ribosome inhibitor antibiotics
***has residual toxicity due to effects on mitochondrial ribosomes (more similar to bacterial ribosomes)

24
Q

Counterpart of eIF4E in bacteria?

A

None, bacteria has no cap

25
Q

Counterpart of eIF2 in bacteria

A

IF2

26
Q

Counterpart of eIF4G in bacteria

A

None, initiation is fundamentally different

27
Q

Counterpart of eEFIA in bacteria

A

EFTu

28
Q

Counterpart of eEF2 in bacteria

A

EFG

29
Q

What are micro RNAs (miRNAs)

A

Short RNA molecules that base pair with mRNAs and inhabit translation

30
Q

Mechanism of miRNAs

A

-initiate form of RISC complex which impedes translation, initiation
-inhibits ribosome from getting any further, physical blockade of initiation complex
–>correlates with many diseases
3’ UTR: where regulation happens

31
Q

Iron homeostasis regulated by ___

A

IRP in 5’ UTR
Low levels of iron >. IRP binds IRE > prevents translation of ferretin

  • iron is a potent oxidant and need to bind it to ferretin
  • if we have low levels of iron, don’t want to bind it to ferretin, production of ferretin tightly correlated with level of iron in cell
32
Q

3 mechanisms of post transcriptional regulation of translation

A

1) mRNA editing
2) miRNAs
3) nutritional status

33
Q

What happens to eIF2 when nutritionally deprived

A

EIF2 is phosphorylated & translation inhibited

We need eIF2B (a GEF that allows eIF2 to bind after hydrolysis)
-poor nutrition, eIF2 is phosphorylated & inactive eIF2B binds and no protein synthesis (non productive complex), reduces effective concentration of EF2B

If reducing concentration of eIF2B, there’s more eIF2 than eIF2B in cell

34
Q

Why are GEFs required

A

Affinity for GDP»>GTP

G protein eIF2 needs GEF to re-assist in binding GTP after hydrolysis

35
Q

What does mTOR path do in response to hypoxia and how

A

MTOR path represses translation in response to hypoxia via eIF4E (the 5’ cap binder)

~it up regulates translation during growth, down regulates during stress

36
Q

During normoxia mTOR phosphorylated ____

A

4EBP-1

37
Q

What does 4EBP-1 do

A

Binds eIF4E to inhibit translation

When it’s phosphorylated, can’t bind and translation proceeds

High mTOR activity in cancer, bc all 4EBP phosphorylated and translation rate very high

38
Q

What happens during hypoxia

A

MTOR reduced, 4EBP-1 phosphorylation reduced, binds eIF4E and impedes translation

39
Q

Selenocysteine is essential for

A

TH production, specifically devoid ashes

40
Q

What is enzymatic ally converted t selenocysteine

A

Serine

-selenocystein has its own tRNA, uses a stop codon (UGA), it’s recoded to allow SEC-tRNA binding

41
Q

What protein is necessary for recoding of stop codon to selenocystein

A

SBP2

42
Q

Rare forms of hypothyroidism causes by

A

SBP2 mutation –>reduced Sec incorporation and decreased production of deiodinases

43
Q

What is eEFSec

A

Specialized elongation factor, binds to Sec-tRNA

Similar to eEFIA

44
Q

Sec-tRNA

A

Specialized tRNA, recognizes UGA codons, carries selenocystein amino acid

45
Q

SECIS

A

RNA sequence in 3’ UTR

Required for Sec incorporation

SBP2 (SECIS. Binding protein 2) binds to SECIDS and assists in getting eEFSec tertiary complex to ribosome at UGA Sec codons

46
Q

What is responsible for creating more than one protein from a single mRNA

A

Ribosomal frame shifting

-pseudo knot tells ribosome to stop & it goes back to slippery site

Frame shift signals: RNA pseudo knot & slippery site

47
Q

Selenocystein encoded by ____ and has been re corded to allow Sec-tRNA binding, ____ is required for this recoding process

A

1) UGA stop codon

2) SBP2 protein

48
Q

Pathogens is of C. Diphtheria with

A

Membrane receptor recognizes and binds toxin ->toxin enters via receptor mediated endophytes is -> toxin dissociates into 2 fragments -> fragment A translocation to cytosol & catalyes transfer of ADPR from NAD + to EF2 –> EF2 inactivated and peptide synthesis stops

49
Q

How does diptheria toxin targets translation

A

Modifies elongation factor responsible to translocation

eEF2 (what pushes from A site to P site)

BMS (7 decks)

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