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Virology > Lecture 9 - (-)-Sense RNA Viruses > Flashcards

Lecture 9 - (-)-Sense RNA Viruses Flashcards

1
Q

Which Baltimore class have (-)RNA genomes, which they transcribe to (+)RNA?

A

Baltimore V

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2
Q

Which Baltimore class has dsRNA genomes, which they use to transcribe to (+)RNA?

A

Baltimore III

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3
Q

Examples of Baltimore V

A

Rhabdoviridae
Filoviridae
Orthomyxoviridae
Paramyxoviridae

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4
Q

Examples of Baltimore III

A

Reoviridae

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5
Q

To which Baltimore class do Rhabdoviridae and Filoviridae belong to?

A

Baltimore V

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6
Q

Which Baltimore class does Reoviridae belong to?

A

Baltimore III

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7
Q

Two broad genome types of Baltimore V viruses

A

1) Segmented genome

2) Non-segmented genome (unimolecular)

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8
Q

First action of a Baltimore V virus upon entering a host cell

A

RDRP within capsid used to make mRNA from genome

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9
Q

Example of segmented genome

A

Orthomyxoviridae

Bunyaviridae

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10
Q

Example of non-segmented genome

A

Paramyxoviridae

Rhabdoviridae

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11
Q 
Basic outline of (-)RNA replication
1)
2)
3)
4)
A

1) (-)RNA used to make (+)RNA, using capsid RDRP
2) (+)RNA makes protein.
3) Replicative protein make (-)RNA (genomic)
4) Structural protein package (-)RNA genome to make virions

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12
Q

Template genome in Baltimore V viruses

A

(-)RNA

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13
Q

Influenza polymerase complex

A

PA, PB1, PB2

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14
Q

Examples of rhabdoviridae

A

Rabiesvirus

Vesicular stomatitis virus

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15
Q

vesicular stomatits virus

A

1) Rhabdoviridae

2) Single, (-)RNA unimolecular genome

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16
Q

Transcriptional regulation in unimolecular (-)ssRNA viruses
1)
2)
3)

A

1) Genes are separated by termination and polyadenylation (UUU…) sequences. Start sequence for the following gene
2) RNA polymerase have a high chance of disengaging from genome at each intergenic region. The chance of RNA polymerase re-engaging reduces the further transcription proceeds through the genome.
3) Therefore genes located at the 3’ end of (-)RNA genome are transcribed and translated at the highest levels, as this becomes the 5’ end of mRNA.

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17
Q

Where are structural genes often located on (-)ssRNA genomes?

A

On the 3’ end

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18
Q

Where are polymerases often located on (-)ssRNA genomes?

A

On the 5’ end

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19
Q

U7 sequence

A

Sequence of 7 U between genes on (-)RNA genomes.

This is transcribed as 7A on mRNA. Often, RNA polymerase will add up to 200 A’s, resulting in a poly-A tail

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20
Q

Function of U7 sequence

A

Leads to poly-A tail formation on mRNA

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21
Q

Examples of henipavirus

A

Hendravirus

Nipahvirus

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22
Q

To what genus do hendravirus and nipahvirus belong to?

A

Henipavirus

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23
Q 
How do henipaviruses regulate gene expression?
1)
2)
3)
4)
A

1) P protein is an essential piece of RNA polymerase
2) C protein and V genes lie within P gene
3) V protein is transcribed when a string of G is read by RNApol, RNApol adds an additional G, shifting the reading frame.
4) C protein is made when a second AUG codon downstream of the AUG to make P is read by RNApol.

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24
Q

Genes occupying the same position on genome of nipahvirus

A

P, C and V proteins.

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25
Q

Role of the C protein in nipahvirus

A

Blocks IFNa/b signalling.

26
Q

Role of V protein

A

Blocks IFNa/b production

27
Q

Viral protein that blocks IFNa/b production

A

V protein (nipahvirus)

28
Q

Viral protein that blocks IFNa/b signalling

A

C protein (nipahvirus)

29
Q

How is the nipahvirus C protein transcribed?

A

Leaky scanning (RNRP binds second AUG)

30
Q

How is the nipahvirus V protein transcribed?

A

mRNA editing. RDRP adds an additional G to a poly-G tract

31
Q

Measlesvirus nucleoprotein size

A

60kDa

32
Q

Measlesvirus nucleoprotein function

A

Self-assembles into a ribonucleoprotein nucleocapsid, by binding to RNA genome, phosphoprotein and RDRP.

33
Q

Where on measles genome is the nucleoprotein gene?

A

3’ end (most transcribed and translated protein)

34
Q

How is measlesvirus genome transcription modulated between mRNA production and genome-length RNA?

A

High levels of N (nucleoprotein) binding to intergenic junctions promotes RDRP readthrough and production of full-length (+)RNA genome template

35
Q

Factor that determines whether mRNA or genome-length (+)RNA genomic template is made from measlesvirus genome?

A

N (nucleocapsid) protein concentration

36
Q

Influenza genome structure
1)
2)
3)

A

1) Eight segments.
2) Each (-)RNA segment is bound to RNA polymerase (PA, PB1, PB2)
3) Each segment is coated in nucleocapsid protein (NP)

37
Q

Influenza envelope proteins

A

Haemagglutinin, neuraminidase, M2 ion-channel protein, NEP (or NS2).

38
Q

Gene arrangement on influenza genome

A

Each of the eight segments encodes 1 gene, except for segments seven and eight, which both encode two genes (different genes expressed by alternative splicing)

39
Q

NS1 in influenza

A

Non-structural protein

40
Q

Signal that is vital for influenza proteins

A

Nuclear localisation sequence

41
Q

Why does influenza need to replicate in the nucleus?

A

Lacks methyl transferase

42
Q

Only (-)RNA virus that doesn’t replicate in the cytoplasm

A

Influenza

43
Q 
Influenzavirus replication
1)
2)
3)
4)
5)
6)
7)
8)
9)
A

1) Sialic acid bound, RME
2) Eight genome segments released into cytoplasm, translocate to the nucleus
3) Viral RDRP makes capped (+)RNA from genome
4) Translation. mRNAs for envelope glycoproteins and M2 ion channel are translocated to the ER-Golgi compartment
5) All proteins are translated into the cytoplasm except for nucleoprotein and RDRP complex (PA, PB1, PB2)
6) Full-length, uncapped, (+)RNA replicative intermediate segments are made, which are templates for (-)RNA genomes
7) M1 and NS1 move to nucleus. M1 binds new (-)RNA, prevents viral mRNA synthesis. Promotes movement of nucleocapsid-coated genome to cytoplasm
8) HA, NA, M2 translated into Golgi, incorporated into cell membrane
9) Nucleoprotein complexed with RNRP, M1, NEP, bud from cell membrane as new virions

44
Q

How does influenza place caps on mRNA if it encodes no methyl transferase?
1)
2)
3)

A

‘Cap snatching’

1) PB1 of RDRP complex binds 5’ terminal sequence of influenza genome (highly-conserved)
2) This activates PB2. When cap of host cell mRNA binds to PB2, influenza (-)RNA cyclises.
3) PB2 binds Cap. Cap is cleaved form cellular RNA by PB1, acts as a primer for viral mRNA synthesis

45
Q

How does influenza regulate whether mRNA or genomic RNA is produced from genome?

A

1) Viral nucleoprotein levels increase, NP binds to viral RNA preventing PB2 from being able to cap it.
2) PA mediates viral RNA replication, whereas PB2 mediates viral mRNA synthesis

46
Q

Ambisense genome

A

Both genomic and anti-genomic strands encode protein

47
Q

What are all ambisense viruses?

A

Segmented, (-)RNA

48
Q

Genera of ambisense viruses

A

1) Arenavirus
2) Phlebovirus
3) Tospovirus
4) Tenuivirus

49
Q

Family of ambisense viruses

A

Bunyaviridae

50
Q

Diseases caused by bunyaviruses and arenaviruses

A

Haemorrhagic fevers

51
Q

Bunyavirus and arenavirus genomes

A

Ambisense, (-)RNA, Two or three segments

52
Q

Example of an arenavirus

A

Lassavirus

53
Q

Genes encoded on arenavirus segment

A

1) (+) sense strand - Z protein

2) (-) sense strand - L protein

54
Q

Ambisense virus transcription and replication
1)
2)

A

1) RNA folds into hairpins that act as extremely strong stop signals
2) When there is enough N protein, readthrough of stop codons is allowed, forming full-length RNAs

55
Q

Viruses with segmented dsRNA genome

A

Reoviridae

56
Q

Example of a reovirus

A

Rotavirus

57
Q

Number of gene segments of rotavirus

A

10 genome segments

58
Q

dsRNA virus replication

A

1) Reoviridae transcribe and replicate dsRNA genome within a protein core. This prevents cell detecting dsRNA and mounting an IFN response

59
Q

Primary and secondary transcription of rotavirus

A

1) Primary - Within core, produces mRNA from genome. This occurs upon entry into host cell.
2) Secondary - Upon assembly of capsid. Forms dsDNA from (+)RNA strand

60
Q

Family to which henipaviruses belong

A

Paramyxoviridae

Virology (29 decks)

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