Lecture 3 and 7 part IV: details of transcription and translation

eIF-2 cycle

The energy needed to stimulate the formation of the 80s initiation complex comes from the hydrolysis of the GTP bound to eIF-2

initiator tRNA

Special tRNA that initiates the translation of an mRNA in a ribosome. It always carries the amino acid methionine.

eIF3 function

Aids in the dissociation of ribosomal subunits

eIF-4F subunits

EIF-4E (binds mRNA = CAP BINDING)
EIF-4A (has ATPase dependent helicase activity = HELICASE)
EIF-4G (aids the binding of the 43S preinitiation complex = SCAFFOLDS mRNA)

eIF-5

promotes binding of 60S to 48S complex

Translation initiation complex

the union of mRNA, initiator tRNA, a small ribosomal subunit, and a large ribosomal subunit

4E-BP

Inhibitor of translation initiation factor eIF4E.
Competes with eIF-4G for binding to eIF-4E

eIF-4G

brings 3' polyA tail and 5' cap together

along with eIF-4E, begins to assemble initial complex with small rRNA subunit -> initial methionine will be positioned at P site

Super important, works as a scaffold

PABP

Poly(A) binding protein stabilizing mRNA, connects the 5´and 3´ends

IRES translation initiation

Allows the virus to escape translation shutdown by cleavage of eIF-4G, by not using this mechanism

IRES domains

II
IIIb
IIIa
IIIc
IIId
IIIe
IV

IRES IIIa structure function

A subdomain required for binding the eIF3 and 40S

IRES IIIb structure function

It's a binding site for eIF3

IRES IIIc, IIId, and IIIe structure function

Binding the 40S subunit

Domains II and IV function

Elements that interact with 40S subunits and are required for accurate placement of the coding region in the decoding side of 40S

Interferons (IFNs)

interfere with viral infections of host cells by inhibiting any translation

Post translational processing of eukaryotic proteins and viral proteins

Glycosylation
Phosphorylation
Proteomics cleavage of polyprotein to produce individual viral proteins

proteolytic cleavage

Cleavage of linker regions in large polyproteins to produce separate proteins