[W5] Mononegavirales

Question 1

What order do mononegaviruses belong to?

Answer 1

Mononegavirales

Question 2

Name four important human-infecting families within Mononegavirales.

Answer 2

• Filoviridae
• Paramyxoviridae
• Pneumoviridae
• Rhabdoviridae

Question 3

Give two examples of viruses from the Filoviridae family.

Answer 3

• Ebola virus
• Marburg virus

Question 4

Name four viruses from the Paramyxoviridae family.

Answer 4

• Measles
• Mumps
• Nipah
• Parainfluenza

Question 5

Which virus is an example from the Pneumoviridae family?

Answer 5

Respiratory syncytial virus (RSV)

Question 6

Name two viruses from the Rhabdoviridae family.

Answer 6

• Rabies virus
• Vesicular Stomatitis Virus (VSV)

Question 7

What symmetry and structure do mononegaviruses have?

Answer 7

Helical ribonucleocapsid surrounded by an envelope with spike proteins (peplomers)

Question 8

What type of genome do mononegaviruses possess?

Answer 8

Negative-sense single-stranded RNA (-ssRNA), non-segmented

Question 9

Why is the mononegavirus genome non-infectious on its own?

Answer 9

Because it is -ssRNA and requires viral proteins like RdRp to initiate transcription

Question 10

What are the characteristics of the genome ends in mononegaviruses?

Answer 10

The genome has 3’ and 5’ UTRs but no 5’ cap or 3’ poly-A tail, and is not covalently linked to a protein

Question 11

What Baltimore group do mononegaviruses belong to?

Answer 11

Group V

Question 12

How many proteins can the genome of mononegaviruses encode?

Answer 12

5 to 11 proteins

Question 13

What is the general gene order in mononegaviruses?

Answer 13

3’-N-P-M-G-L-5’

Question 14

What is the function of the nucleoprotein (N)?

Answer 14

Protects the RNA genome

Question 15

What is the function of the phosphoprotein (P)?

Answer 15

Binds N and L proteins; part of the RNA polymerase complex

Question 16

What does the matrix protein (M) do?

Answer 16

Maintains virion structure and connects the nucleocapsid to the envelope

Question 17

What is the function of the fusion factor (F)?

Answer 17

Mediates fusion between the viral envelope and host cell membrane

Question 18

What do HN, H, and G proteins function as?

Answer 18

Viral attachment proteins

Question 19

What is the function of the large protein (L)?

Answer 19

RNA-dependent RNA polymerase

Question 20

What is the shape and genome size of Filoviridae?

Answer 20

Filamentous; genome size 18–19 kb

Question 21

How long are Marburg and Ebola viruses?

Answer 21

• Marburg: ~790 nm
• Ebola: ~970 nm

Question 22

How many proteins does the Ebola virus genome encode?

Answer 22

7 proteins

Question 23

What is the shape and genome size of Paramyxoviridae?

Answer 23

Spherical; ~150 nm in diameter; genome size ~15 kb

Question 24

How many proteins does Measles virus encode?

Answer 24

8 proteins

Question 25

What is the shape and genome size of Pneumoviridae?

Answer 25

Spherical; ~150 nm; genome size ~15 kb

Question 26

How many proteins does RSV encode?

Answer 26

11 proteins

Question 27

What is the shape and size of Rhabdoviridae virions?

Answer 27

Bullet-shaped; 180 nm long × 75 nm wide

Question 28

What family does rabies virus belong to?

Answer 28

Rhabdoviridae

Question 29

How is rabies virus transmitted?

Answer 29

Through animal bites

Question 30

What is the morphology of rabies virus?

Answer 30

Enveloped, bullet-shaped, 180 × 70 nm

Question 31

What is the genome of rabies virus?

Answer 31

-ssRNA genome, 11–15 kb, with RdRp packaged in the virion

Question 32

Outline the dissemination pathway of rabies virus.

Answer 32

Entry → muscle → peripheral neurons → CNS → brain → salivary glands → saliva

Question 33

How long can the incubation period of rabies be?

Answer 33

3–12 weeks

Question 34

What are the 9 steps of the mononegavirus replication cycle?

Answer 34

* Attachment * Fusion * Uncoating * Primary transcription/translation * Antigenome synthesis * Genome replication * Secondary transcription/translation * Assembly * Release

Question 35

What determines viral attachment to a host cell?

Answer 35

Interaction with specific cell surface receptors

Question 36

How does MuV attach to host cells?

Answer 36

Via HN protein binding to sialic acid

Question 37

How does Measles virus bind to cells?

Answer 37

Via SLAM (CD150), nectin-4, and CD46

Question 38

What is the role of the fusion (F) protein?

Answer 38

Facilitates fusion between viral and host membranes

Question 39

How are F proteins activated in mononegaviruses?

Answer 39

Either by receptor binding or endosomal acidification

Question 40

What occurs during uncoating?

Answer 40

Genome and RdRp are released into cytoplasm

Question 41

Why must RdRp be packaged in the virion?

Answer 41

Because -ssRNA cannot be directly translated

Question 42

Where does transcription begin on the genome?

Answer 42

At the 3’ end

Question 43

What enzymatic activity adds a 5’ cap?

Answer 43

PRNTase activity of RdRp

Question 44

What is polymerase stuttering?

Answer 44

Slipping back of RdRp to add extra adenines, creating a poly-A tail

Question 45

What is transcription polarity in mononegaviruses?

Answer 45

Gradient of mRNA abundance from 3’ to 5’ due to sequential transcription

Question 46

Which genes are most abundantly transcribed?

Answer 46

Genes near the 3’ end (e.g., nucleocapsid protein gene)

Question 47

What is mRNA editing in mononegaviruses?

Answer 47

Co-transcriptional insertion of extra residues by RdRp causing frame shifts

Question 48

How do filoviruses use mRNA editing?

Answer 48

To produce different forms of glycoproteins

Question 49

What is sGP and its function?

Answer 49

A secreted form of GP involved in immune evasion

Question 50

What machinery translates viral mRNAs?

Answer 50

Host cell ribosomes

Question 51

What triggers genome replication?

Answer 51

High concentration of nucleocapsid protein (N)

Question 52

What is the antigenome?

Answer 52

Full-length +ssRNA used to make -ssRNA genomes

Question 53

Where are spike proteins synthesized?

Answer 53

On the rough endoplasmic reticulum (RER)

Question 54

How is the F0 fusion protein activated?

Answer 54

It is cleaved into F1 and F2 by host furin in the trans-Golgi

Question 55

What role does matrix (M) protein play in assembly?

Answer 55

Organizes assembly and recruits ribonucleoprotein

Question 56

How do virions acquire their envelope?

Answer 56

By budding from the host cell membrane

Question 57

What host machinery aids in viral budding?

Answer 57

ESCRT (Endosomal Sorting Complex Required for Transport) machinery

Question 58

Why do mononegaviruses mutate rapidly?

Answer 58

Due to the lack of proofreading by RdRp

Question 59

What is the mutation rate during replication?

Answer 59

Up to 1 mutation per 1,000 bases

Question 60

How does high mutation rate benefit mononegaviruses?

Answer 60

Increases diversity and helps evade immune responses