Chapter 12: Regulation of Translation

Question 1

Translation rates respond to the () of the cell, reflected in the amount of amino acids present

Answer 1

nutritional state

Question 2

In bacteria, () compete with charged tRNAs for binding at the A site

Answer 2

uncharged tRNAs

Question 3

binding of uncharged tRNA in A site of bacterial ribosome results in recruitment of ()

Answer 3

RelA

Question 4

RelA synthesizes lots of (p)ppGpp (a pentaphosphate guanine nucleotide called “()”) from GTP/GDP and ATP precursors.

Answer 4

magic spot

Question 5

action of RelA modulates transcription and induces stress responses to replenish amino acids. This is called the “()”

Answer 5

stringent response

Question 6

In eukaryotes, the uncharged tRNA binds to ();

Answer 6

Gcn2

Question 7

When bound to tRNA, a kinase domain in Gcn2 phosphorylates the initiation factor () in euks.

Answer 7

eIF2

Question 8

Phosphorylated eIF2 binds strongly to () (to the point where active eIF2 is effectively depleted from the cell), and cannot then be used for initiation, so translation is shut dow

Answer 8

eIF2B

Question 9

Normally, eIF2 binds to eIF2B and exchanges ()

Answer 9

GDP for GTP

Question 10

Phosphorylation at () results in constitutive binding of eIF2 to eIF2B, inhibiting translation initiation

Answer 10

serine 51 of the eIF2 alpha subunit

Question 11

mRNAs compete for ()–this is another opportunity for translational regulation

Answer 11

translation machinery

Question 12

eIF4E can be sequestered by a range of () in response to cellular conditions- this decreases overall translation activity

Answer 12

4E-BPs (eIF4E – Binding Proteins)

Question 13

mRNAs assume () in different conditions–and these affect translation levels

Answer 13

different shapes

Question 14

In bacteria,the Shine-Dalgarno sequence is often (), preventing translation initiation

Answer 14

obscured

Question 15

() are another example-these small regulatory molecules control their own synthesis

Answer 15

Riboswitches

Question 16

one riboswitch example is ()

Answer 16

thiamine synthesis

Question 17

Another example of regulated SD sequestration mediated by protein: control of the expression of () in E.coli

Answer 17

threonine tRNA synthetase

Question 18

5′UTR regulation is less common in eukaryotes, but is used for ()

Answer 18

iron regulation

Question 19

Too much free iron is toxic, so iron is tightly bound to () (storage protein)–the higher the iron concentration, the more () is needed

Answer 19

ferritin

Question 20

The 5′ UTR of ferritin mRNA has (1) that bind to (2)

Answer 20

1. Iron Response Elements (IREs)
2. Iron Regulatory Proteins (IRPs)

Question 21

Gcn4 is a transcription activator of many amino acid synthesis genes -> its translation is activated by ()

Answer 21

cellular starvation

Question 22

While eukaryotic 5’ UTR is relatively small in comparison to bacteria, eukaryotic () are large and regulation using these sequences is common, particularly in developmental regulation.

Answer 22

3′ UTRs

Question 23

3’ UTRs can be the driving force in regulating gene expression in certain ().

Answer 23

developmental programs

Question 24

In Xenopus laevis oocytes, maternally-derived mRNAs are not initially translated – they are ()

Answer 24

dormant, or translationally repressed

Question 25

activation of translationally repressed mRNA in X. laevis depends on the ()

Answer 25

3' UTR poly(A) tail length

Question 26

The 3′ UTR cytoplasmic polyadenylation element (CPE) is bound by ().

Answer 26

CPEB

Question 27

CPEB sequesters () via other proteins (i.e. Maskin), and this stops formation of the closed loop required for translation initiation

Answer 27

eIF4E

Question 28

() is a type of 4E-BP that has additional specificity for CPEB.

Answer 28

Maskin

Question 29

Dormant mRNAs are activated by phosphorylation of CPEB by kinase ().

Answer 29

Eg2

Question 30

Phosphorylated CPEB recruits ().

Answer 30

CPSF (cytoplasmic polyadenylation specificity factor)

Question 31

CPSF binds to standard AAUAAA polyadenylation signal and recruits () to the mRNA which eventually leads to the extension of the poly(A) tail

Answer 31

poly(A) polymerase (PAP)

Question 32

() may also regulate translation in eukaryotes by binding partly complementary sequences in the 3ʹ UTR

Answer 32

microRNAs (miRNAs)

Question 33

phosphorylation of eEF2 in response to stress leads to accumulation of () which inhibits elongation

Answer 33

pre-translocation-state ribosomes

Question 34

Elongation regulation often accompanies () to help cells preserve and redirect limited resources under difficult conditions.

Answer 34

initiation regulation

Question 35

Many of these battles between host and virus are fought in the initiation step ()

Answer 35

disrupting cap-dependent initiation

Question 36

Picornaviruses (like polio) disrupt the formation of the host closed loop complex by ()

Answer 36

protein cleavage

Question 37

Flu viruses disrupt closed-loop formation by ()

Answer 37

cleaving the 5′ cap

Question 38

Encephalomyocarditis (another picornavirus)encodes proteins that (), leading to sequestering of eIF4E and disruption of initiation

Answer 38

dephosphorylate the 4E-BPs

Question 39

Picornaviruses inhibit cap-dependent translation, so they themselves use cap-independent translation by using () within the 5′ UTR to directly recruit ribosomes

Answer 39

Internal Ribosome Entry Sites (IRES)

Question 40

when binding to IRES (kind of analogous to Shine-Dalgarno) picornaviruses do not depend on eIF4 factors that it has destroyed, but rather utilizes ()

Answer 40

IRES-transacting factors (ITAFs)

Question 41

Viruses can also simply compete for limited ()

Answer 41

translation factors

Question 42

in euks., () phosphorylates eIF2 when activated by the presence of double-stranded viral RNA

Answer 42

PKR protein

Question 43

In (): part of the 3′ UTR mimics tRNAVal, which then becomes acylated and initiates translation at an AUG, albeit with a mismatch

Answer 43

Turnip Yellow Mosaic Virus (TYMV)

Question 44

In (): initiation is mediated by base-pairing between 3 nucleotides in the 5′ UTR (AGG) and 3 nucleotides right upstream of an alanine (CCU)

Answer 44

Cricket Paralysis Virus (CrPV)