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MICR2121 Molecular Virology > Virus Genomes and Proteins > Flashcards

Virus Genomes and Proteins Flashcards

1
Q

What are the two ways viruses can encode their genetic information?

A

RNA

DNA

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2
Q

What viruses are RNA + strand and non-enveloped?

A

Picornaviridae

Caliciviridae

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3
Q

What viruses are RNA - strand and enveloped?

A

Togaviridae
Flaviviridae
Coronaviridae
Retroviridae

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4
Q

What viruses are RNA - stranded and enveloped?

A 
Filoviridae
Bunyaviridae
Rhaboviridae
Orthomyxoviridae
Paramyxoviridae
Arenaviridae
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5
Q

What viruses are dsRNA and non-enveloped?

A

Reoviridae

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6
Q

What are facts about RNA viruses?

A

small genomes 3-32Kb
polymerase error prone
mostly single-stranded

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7
Q

Why do RNA viruses not follow the Central Dogma?

A

miss out the DNA step

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8
Q

Facts about positive-sense RNA viruses?

A
  • directly translated
  • share structural features of mRNA - piggy back on host cell machinery
  • often have 5’ cap and 3’ polyA tail
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9
Q

why do eukaryotic mRNAs have the 5’ 7-methylguanoise Cap?

A

resistance to exonucleases

Recognition by translational machinery

longer half life

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10
Q

What is the IRES?

A

genome folds to form RNA secondary structure using H-bonds

act as cap for translation

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11
Q

What is the genome size of flaviviruses and examples?

A

11Kb
Yellow Fever Virus
West Nile Virus
Dengue Fever Virus

5’ cap and 3’ poly A tail

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12
Q

What is the genome size of picornaviruses and examples?

A

7.5Kb
Poliovirus
Rhinovirus
Hepatits A virus

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13
Q

What are features of the picornavirus genome?

A

5’ Vpg
IRES
Single ORF encodes 2200aa polyproteins
Poly(A) tract

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14
Q

What is the genome size of alphaviruses and examples?

A

12Kb
Eastern equine encephalitis virus
Chikungunya virus

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15
Q

What are features of the alphavirus genome?

A

5’ m7G cap
non-structural ORF1
structural ORF2
PolyA tract

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16
Q

What is the genome size of coronaviruses and examples?

A

33Kb
SARS
MERS

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17
Q

What are features of the coronavirus genome?

A

multiple ORFs
5’m7G cap
3’ PolyA tract
‘leader’ sequence

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18
Q

What is the genome size of retroviruses and examples?

A

9-11Kb
Mo-MLV
HTLV
HIV

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19
Q

What are features of the retrovirus genome?

A 
5' cap 
3' polyA tail
LTR
Multiple overlapping ORF's 
replicate via duplex DNA copy
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20
Q

What is the simplified retrovirus replication cycle

A

Reverse transcribed into RNA-DNA hybrid

DNA

integrated into the host genome

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21
Q

What are features of negative sense RNA viruses?

A

genome is REVERSE COMPLEMENT of the coding strand

No cap or PolyA

22
Q

Which negative sense RNA viruses are non-segmented?

A

Rhabdoviruses
Paramyxoviruses
Filoviruses

23
Q

Which negative sense RNA viruses are segmented?

A

Orthomyxoviruses

Bunyaviruses

24
Q

What is the genome size of rhabdoviruses and examples?

A

6.4Kb
Rabies
VSV

25
Q

What are features of the rhabdovirus genome?

A

PolyU tracts
terminator & promoter sequences

replicated & transcribed into positive RNA molecule

26
Q

What is the genome size of filoviruses and examples?

A

19Kb
Ebola
Marburg

27
Q

What are features of the filovirus genome?

A

highly conserved transcriptional signals at 3’
termination signals at 5’
intragenic regions vary in length

28
Q

Orthomyxovirus examples?

A

Influenza

29
Q

What are features of the Influenza genome?

A

Negative RNA segmented
8 segments
890-2341 bases
common 3’ 5’ termini

30
Q

What human dsDNA viruses are Non-enveloped?

A

Adenoviridae (L)

Papillomaviridae (C)

31
Q

What human dsDNA viruses are enveloped?

A

poxviridae (L)
Herpesviridae (L)
Hepadnaviridae (C)

32
Q

What human ssDNA viruses are nonenveloped?

A

parvoviridae (C)

33
Q

What are features of DNA Virus genomes?

A
  • Origins of DNA replication
  • Promoters/enhancers - drive transcription of viral genes
  • DNA replication & transcription - temporally controlled
  • viral mRNAs spliced
  • overlapping genes
34
Q

What is the genome size of adenoviruses?

A

duplex DNA genomes up to 36Kb

35
Q

What are features of the adenovirus genome?

A 
ITR 100-140bp
Terminal protein (TP) linked to 5' ends (primer)
36
Q

What is the size of herpesvirus genome?

A

150Kb

37
Q

What are features of the herpesvirus genome?

A

4 isomers
3 origins of DNA replication
80 virus encoded proteins
temporally controlled gene expression

38
Q

What is the genome size of papillomaviruses and examples?

A

8Kb

HPV

39
Q

What are features of the papillomavirus genome?

A

early & late expressing genes

Overlapping reading frames - transcribed at different stages

40
Q

What are virus structural proteins?

A

protect the nucleic acid genome
co-ordinated assembly
Mechanism for delivery of genome to new cell

41
Q

What are capsid proteins?

A

highly positively charged
rich in arginine & lysine
package nucleic acid
self assemble - helical & icosahedral

42
Q

What are picornavirus capsid proteins?

A
  • 4 proteins from building block of capsid
  • 60 form icosahedral capsid
  • negative charge of RNA counteracted by Na+/K+ ions
43
Q

What are Matrix proteins?

A
  • only enveloped viruses

- interact with capsid & envelope proteins

44
Q

What are viral glycoproteins?

A

recognise specific receptors

Mediate fusion between viral & cellular membranes

protection from immune system

45
Q

How are glycoproteins synthesised?

A

Addition of N-acetylglucosamine to Asn-X-Ser/Thr

Transport to Golgi

Glycan processing

Transport to plasma membrane

Expression on cell surface

46
Q

How are viral glycoproteins matured?

A

Proteolytic cleavage by cellular enzyme e.g. Furin

47
Q

What are virus non-structural proteins?

A
  • Produced within infected cell
  • replication of virus nucleic acids
  • assembly of virus particles
  • regulation of host cells
48
Q

What are viral polymerases?

A

Enzymes involved in genome replication

encode own

catalyse replication of viral genome

tagets for anti-viral drugs

49
Q

What type of proteins are required for genome replication?

A

accessory proteins

encode helicase enzymes

unwind duplex DNA/RNA

Requires energy

requires NTPase activity

50
Q

What are viral proteases?

A

cleaves polypeptides chains - specific aa

polyproteins sometimes need to be cleaved further

polyprotein processing

51
Q

What way to viral proteases cleave in?

A

in cis and in trans

52
Q

What are regulatory proteins?

A

play a role in survival

transforming proteins

interfere with immune response

interfere with host cell metabolism - help viral replication

MICR2121 Molecular Virology (15 decks)

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