Negative Strand RNA Viruses

Question 1

What are the non-segmented negative RNA viruses?

Answer 1

Filoviruses
paramyxoviruses 
pneumoviruses 
Rhabiroviruses 
Bornaviruses

Question 2

What are the segmented negative negative RNA viruses?

Answer 2

Bunyaviruses

Orthomyxoviruses

Question 3

Examples of filoviruses?

Answer 3

Ebola
Marburg viruses
transmitted by fluids

Question 4

Examples of Pneumoviruses?

Answer 4

Human respiratory syncytial virus

No vaccine

200k deaths per year

Question 5

Examples of paramyxoviruses?

Answer 5

Measles virus
systemic infection
vaccine but still 500k deaths per year

Question 6

Examples of rhabdovirus?

Answer 6

Rabies virus
60k deaths
transmitted via dog & bat bites

Question 7

What are the 3 defining characteristics of neg strand RNA viruses?

Answer 7

1 - genome is non-coding
2 - RNA polymerase
3 - genome is not naked

Question 8

What is the RNP?

Answer 8

RNA genome covered end-to-end
RNA becomes ordered into helical structure
RNA in RNP is resistant to RNase

Question 9

How does N bind the RNA genome?

Answer 9

Rhabdovirus N protein & RNA forms rings

N-RNA interacts via phosphate backbone via K & R amino acids

Question 10

What does RNP structure look like when imaged by cryo-EM?

Answer 10

RNA tightly hidden in a cleft

3 N molecules + RNA

Question 11

Why is VSV a good model virus?

Answer 11

just 5 genes 
rapid growth
easy to purify 
very stable 
not human pathogen

Question 12

What are the 5 genes of VSV?

Answer 12

Nucleocapsid protein - wraps RNA into RNP helix
Phosphoprotein - RdRp cofactor
Matrix protein - links N with G
Glycoprotein - spikes
Large protein - RNApol

Question 13

what is the mRNA transcription?

Answer 13

neg sense copied into pos sense mRNAs by RdRp

pos sense mRNAs translated on host cell ribosomes

Question 14

What are the 3 basic stages of VSV transcription?

Answer 14

1 - RdRp binds to genome at 3’ end
2 - RdRp locates at gene start - copies template into pos strand RNA
3 - RdRp responds to signals in genome to stop copying

Question 15

What are the transcription signals in VSV?

Answer 15

start signal - AACAG
Stop signal - AUACUUUUUUU

gene junctions with both with a space in-between the stop and start

RdRP responds to these signals - one mRNA per gene

Question 16

What causes the gradient of transcription?

Answer 16

1 - SINGLE 3’ RdRp entry site
2 - RdRp can only move in one direction
3 - RdRp can fall off the template at GENE JUNCTIONS

Question 17

What are the 3 major DIFFERENCES of RNA replication to transcription?

Answer 17

1 - copying starts at extreme end of the template - RdRp binds at 3’ end & first nucleotide to be copied is position1, in transcription its pos44

2 -RdRp ignores gene junctions in replication - in transcription RdRp stops

3 - New antigene is wrapped in N protein - in transcription the mRNAs are naked

replication occurs AFTER transcription in VSV

Question 18

How can weak viruses for vaccines be made?

Answer 18

change position of certain genes so they are expressed at a lower level

e.g. Ebola vaccines - N moves to 4th position