Translation

Question 1

What are the roles of the ribosomal subunits?

Answer 1

Small ‘reads’ RNA

Large joins AAs

Question 2

Describe the movement of a ribosome.

Answer 2

5’ to 3’

New AAs delivered to C terminus of polypeptide.

Question 3

What four ways can eIF4 E be regulated and what is its function?

Answer 3

Phosphorylation
Over expression 
Elevated 
Binding proteins
Binding protein expression. 

Binds 5’ cap of mRNA

Question 4

Outline the wobble hypothesis.

Answer 4

3’ position of codon allows non-Watson-Crick base pairing.

Reduces number of tRNA species needed to decode a codon.

(Only need 31 but have ~45)

Question 5

How does the ribosome size change during initiation?

Answer 5

40S
Associates with eIFs –> 43S
Targeted to end of mRNA –> 48S
Scans mRNA for AUG

60S associates, Met-tRNA attached, eIFs dissociate.

Question 6

How are tRNAs delivered to the ribosome?

Answer 6

Attached to elongation factor eEF1.

Question 7

How is elongation regulated?

Answer 7

Phosphorylation eEF2

By MAPK kinase cascade

PKA (response to starvation, hypoxia, stress)

Cell cycle regulatory proteins.

Question 8

What ways can the cell cycle regulate translation?

Answer 8

EIF4E phosphorylation reduced

EIF2 alpha phosphorylation increased

EEF2 phosphorylation increased

Question 9

How can viruses affect translation?

Answer 9

Induce stress response.

Poliovirus and EMCV inhibit translation by cleaving eIF4G and PABP.