RNA multiplication

Question 1

Steps of transcription, translation + NA replication: Double-stranded RNA viruses (dsRNA)

Answer 1

1. Transcription
2. Translation
3. Replication
4. Late transcription, translation

Question 2

Double-stranded RNA viruses (dsRNA): Characteristics of multiplication

Answer 2

An alien nucleic acid for the cell

• Intensive interferon response
• Partial decapsidation

Question 3

Double-stranded RNA viruses (dsRNA): Examples

Answer 3

• Reoviridae
• Birnaviridae

Possess a segmented genome

Question 4

Double-stranded RNA viruses (dsRNA): Transcription

Answer 4

• dsRNA not readable for the ribosomes
• Viral RdRp - structural:
  
  • Transcription mode → mRNA synthesis

Question 5

Double-stranded RNA viruses (dsRNA): Translation

Answer 5

Monocistronic coding:

• Segment → protein

Question 6

Double-stranded RNA viruses (dsRNA): Replication

Answer 6

• mRNA enters the inner capsid
• Viral RdRp in replicase mode
  
  • mRNA supplemented with a negative thread

Question 7

Double-stranded RNA viruses (dsRNA): Late transcription, translation

Answer 7

Assembly of progeny virions

Question 8

Steps of transcription, translation + NA replication: Single-stranded, positive sense RNA viruses (+ssRNA)

Answer 8

• Transcription
• Translation
• Replication

Question 9

Single-stranded, positive sense RNA viruses (+ssRNA): Transcription

Answer 9

• Genomic RNA → mRNA
  
  • 5’ methyl capped, 3’ polyadenylated
  • Directly attaches to ribosomes

Question 10

Single-stranded, positive sense RNA viruses (+ssRNA): Translation

Answer 10

• Polycistronic mRNA
  
  • Precursor polypeptide
  • Protease cleavage
• Monocistronic mRNA
  
  • Subgenomic mRNA synthesis
  • Structural protein production
  • More accurate synthesis control

Question 11

Give examples of viruses with polycistronic mRNA

Answer 11

• Picornaviruses
• Flaviviruses

Question 12

Give examples of viruses with monocistronic mRNA

Answer 12

• Nidovirales
• Caliciviridae
• Togaviridae

Question 13

Single-stranded, positive sense RNA viruses (+ssRNA): Replication

Answer 13

• Viral replicase

1. Replicative intermediate forms: dsRNA, -ssRNA
2. -ssRNA is the template for the progeny +ssRNA genome
3. Translation from the progeny RNA
4. The + threads incorporate into the progeny virions

Question 14

Single-stranded, positive sense RNA viruses (+ssRNA): Examples

Answer 14

• Picornaviridae
• Calciviridae
• Togaviridae
• Flaviviridae

Question 15

Steps of transcription, translation + NA replication: Single-stranded, negative sense RNA viruses (-ssRNA)

Answer 15

1. Transcription
2. Monocistronic translation
3. Replication

Question 16

Single-stranded, negative sense RNA viruses (-ssRNA): Transcription

Answer 16

• Negative-sense RNA
• Non-readable for the ribosomes
  
  • → Viral RdRp - structural
• Transcription mode
  
  • Complimentary (+) thread synthesis
    
    • → mRNA

Question 17

Single-stranded, negative sense RNA viruses (-ssRNA): Replication

Answer 17

• RdRp in replication mode
  
  • → dsRNA in the nucleocapsid
  • → Full-length +ssRNA synthesis
  • → -ssRNA synthesis
• Finally, negative threads stay in the progeny virions

Question 18

Steps of transcription, translation + NA replication: Viruses using reverse transcriptase

Answer 18

1. Transcription
2. Translation
3. Replication

Question 19

Which viral family uses reverse transcriptase

Answer 19

Retroviridae

Question 20

Viruses using reverse transcriptase: Transcription

Answer 20

Genome uses mRNA but:

• Reverse transcriptase transcribes to → dsDNA

dsDNA integrates into the cellular genome

Cellular transcriptase → mRNA production

Question 21

Viruses using reverse transcriptase: Translation

Answer 21

Polycistronic mRNA - Protease cleavage

Question 22

Viruses using reverse transcriptase: Replication

Answer 22

Transcription

• _​​_mRNA will serve as the genome of the progeny viruses

Question 23

Hepadnaviridae: Circular ss/dsDNA: Transcription

Answer 23

• Repair of the gapped genome: Viral polymerase
• Cellular transcriptase: mRNA production
  
  • Short transcripts → Proteins

Question 24

Hepadnaviridae: Circular ss/dsDNA: Translation

Answer 24

Monocistronic mRNAs

Question 25

Hepadnaviridae: Circular ss/dsDNA: Replication

Answer 25

* Full-length transcripts of 'mRNA' * Maturation: Viral reverse transcriptase produces complementary DNA thread * Circularisation, partly completed to dsDNA

Question 26

Give the importance of eclipse strategies

Answer 26

* Consequences on pathogenesis/epidemiology * Detection of intermediate forms * *In vitro* protein expression studies * Anti-viral drug development * HIV: * Reverse transcriptase inhibitors * Protease inhibitors