Translation (Copeland)

Question 1

3’ UTR is site of

Answer 1

Key regulatory sequences

Question 2

Stop codons

Answer 2

UGA, UAA, UAG

Question 3

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

Answer 3

initiation factors

Question 4

3’ CCA end of tRNA is not ___

Answer 4

Transcribed! It is added after processing

-need CCA end of enzyme can teach

Question 5

Aminoacylation requires

Answer 5

ATP

Question 6

Amino acyl tRNA synthetase

Answer 6

Recognizes tRNAs and adds appropriate amino acid

Question 7

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

Answer 7

Editing site and removed

Question 8

Eukaryotic ribosome properties

Answer 8

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

-3 tRNA binding sites

5’ E P A 3’

Question 9

Initiation and elongation occur

Answer 9

Simultaneously

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

Question 10

What is the most important for regulation of translation?

Answer 10

Initiation

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

Question 11

EIF2

Answer 11

Eukaryotic transcription factor

Binds & delivers initiator Met-tRNA

Question 12

EIF4E

Answer 12

Binds 5’ cap

Question 13

EIF4G

Answer 13

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

Question 14

What causes eIF2 release so 60S subunit can bind?

Answer 14

GTP hydrolysis

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

Question 15

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

Answer 15

Elongation

Question 16

What is eEF1A

Answer 16

Binds all tRNAs except initiator and selenocysteine

• GTP bound to it
• delivery of aa-tRNA

Question 17

How does eEF1A get released

Answer 17

GTP hydrolysis

-incorrectly base-paired tRNAs disassociates

Question 18

What is eEF2

Answer 18

Catalyze so translocation; pushes from Asite to P site

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

Question 19

What causes eEF2 release

Answer 19

GTP hydrolysis

-completion, A space is open for business

Question 20

What is eRF1

Answer 20

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

Question 21

What dictates initiation in bacterial translation

Answer 21

Shine-dalgarno sequence

Question 22

Is 5’ cap required in bacteria

Answer 22

No

Also transcription and translation is coupled

Question 23

Describe bacterial ribosome

Answer 23

-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)

Question 24

Counterpart of eIF4E in bacteria?

Answer 24

None, bacteria has no cap

Question 25

Counterpart of eIF2 in bacteria

Answer 25

IF2

Question 26

Counterpart of eIF4G in bacteria

Answer 26

None, initiation is fundamentally different

Question 27

Counterpart of eEFIA in bacteria

Answer 27

EFTu

Question 28

Counterpart of eEF2 in bacteria

Answer 28

EFG

Question 29

What are micro RNAs (miRNAs)

Answer 29

Short RNA molecules that base pair with mRNAs and inhabit translation

Question 30

Mechanism of miRNAs

Answer 30

-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

Question 31

Iron homeostasis regulated by ___

Answer 31

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

Question 32

3 mechanisms of post transcriptional regulation of translation

Answer 32

1) mRNA editing 2) miRNAs 3) nutritional status

Question 33

What happens to eIF2 when nutritionally deprived

Answer 33

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

Question 34

Why are GEFs required

Answer 34

Affinity for GDP>>>GTP G protein eIF2 needs GEF to re-assist in binding GTP after hydrolysis

Question 35

What does mTOR path do in response to hypoxia and how

Answer 35

MTOR path represses translation in response to hypoxia via eIF4E (the 5' cap binder) ~it up regulates translation during growth, down regulates during stress

Question 36

During normoxia mTOR phosphorylated ____

Answer 36

4EBP-1

Question 37

What does 4EBP-1 do

Answer 37

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

Question 38

What happens during hypoxia

Answer 38

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

Question 39

Selenocysteine is essential for

Answer 39

TH production, specifically devoid ashes

Question 40

What is enzymatic ally converted t selenocysteine

Answer 40

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

Question 41

What protein is necessary for recoding of stop codon to selenocystein

Answer 41

SBP2

Question 42

Rare forms of hypothyroidism causes by

Answer 42

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

Question 43

What is eEFSec

Answer 43

Specialized elongation factor, binds to Sec-tRNA | Similar to eEFIA

Question 44

Sec-tRNA

Answer 44

Specialized tRNA, recognizes UGA codons, carries selenocystein amino acid

Question 45

SECIS

Answer 45

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

Question 46

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

Answer 46

Ribosomal frame shifting -pseudo knot tells ribosome to stop & it goes back to slippery site Frame shift signals: RNA pseudo knot & slippery site

Question 47

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

Answer 47

1) UGA stop codon | 2) SBP2 protein

Question 48

Pathogens is of C. Diphtheria with

Answer 48

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

Question 49

How does diptheria toxin targets translation

Answer 49

Modifies elongation factor responsible to translocation eEF2 (what pushes from A site to P site)