Lec 7 - RNA virus replication 1

Question 1

What are VRCs and what are they made of?

Answer 1

Virus replication complexes are sites of RNA virus replication.
Made of lipids, proteins and genomes from host and virus

Question 2

What is the difference between (+) and (-) RNA viruses?

Answer 2

(+) RNA viruses are directly translatable whereas (-) RNA viruses need RdRp to make mRNA

Question 3

If a RNA virus doesn’t have a 5’ cap, what do they use to mimic one?

Answer 3

Internal ribosome entry site (IRES) with a VPg primer is used instead

Question 4

Compare a normal eukaryotic translation and a viral translation using poliovirus as an example

Answer 4

Normal: eIF4G complex binds 5’ cap and polyA binding proteins (PABS) bind polyA tail
Poliovirus: IRES (5’ cap) bound by host ITAF. eIF4G degraded by virus

Question 5

List the steps in an overview of viral gene expression

Answer 5

1. IRES dependent translation
2. Polyprotein processing
3. VRC formation
4. mRNA and genome synthesis
5. Virion formation

Question 6

Explain suppression of translation termination

Answer 6

Polyproteins with proteins needed less are translated less to conserve energy and components

Question 7

Explain how ribosomal frameshifts are used to translate less abundant polyproteins

Answer 7

3’ pseudoknot pauses ribosomal, creating -1 frameshift which makes slippery sequence. Last nucleotide used again as first nucleotide. 10% cases resolved by backtracking = less abundant polyproteins

Question 8

Describe how SARS-CoV-2 use ribosomal frameshifts in sgRNA translation

Answer 8

sgRNA with leader and body sequences with transcription regulatory sequences (TLRs). RdRp jumps from leader TLR to body TLR to get selective discontinuous translation