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Flashcards in Viruses Deck (13)
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1
Q

How many coat protein subunits does a TMV particle have?

A

2130

2
Q

How does the 20S disk allow recognition of homologous viral RNA?

A

Provides long stretch of nucleotide binding sites for interaction with specific RNA sequence

3
Q

Who discovered the origin of assembly?

A

Zimmern 1977

4
Q

How is viral elongation bidirectional?

A

5’ end is pulled through central hole and rapid elongation ensues
3’ end is slower due to the types of protein aggregates that are used to assemble the particle

5
Q

Co-translational and co-replicational disassembly

A
  • Once inside a plant cell, there is a different pH and concentration of calcium ions, so the coat proteins lose protons and Ca2+ ions
  • Loss of charge results in weakening of the virus coat at the 5’ end
  • Ribosomes bind to the 5’ end and begin moving down the RNA, which strips off the coat proteins
  • The replicase proteins are translated and begin translating from the 3’ end
  • As they replicate the virus, they strip off the remaining coat proteins
6
Q

Brome mosaic virus infectious clone

A

Strong tool for studying plant viruses
Convert positive-sense RNA to double-stranded cDNA using reverse transcriptase
Have cDNA copy of viral genome carried in a bacterial plasmid

7
Q

Brome mosaic virus 3 particles

A

Particle 1: RNA1 - P1 (methyltransferase and helicase)
Particle 2: RNA2 - P2 (RNA polymerase)
Particle 3: RNA3 - P3a and P3b (movement and capsid)
RNA4 - subgenomic P3b/P4 (capsid)

8
Q

Three virus-encoded enzymes involved in replication of positive-sense RNA viruses

A
  1. Helicase - separates and straightens RNA strands during replication
  2. Methyltransferase - transfers 5’ cap to end of viral RNAs
  3. RNA-dependent RNA polymerase
9
Q

What do Potyviruses have at their 5’ end?

A

A protein, no 5’ cap

10
Q

What genome does Cauliflower mosaic virus have?

A

dsDNA, replicated by reverse transcription of a pregenomic RNA

11
Q

Proteins encoded by CaMV genome

A

Cell-to-cell movement protein (P1)
Two aphid transmission factors (P2 & P3)
Precursor of capsid proteins (P4)
Polyprotein precursor of proteinase, reverse transcriptase and ribonuclease H (P5) (separates RNA from cDNA)
Inclusion body protein/translational transactivator

12
Q

CaMV transcription and protein synthesis

A
  • Discontinuities, gaps close in nucleus when dsDNA associated with histones
  • Minichromosome is transcribed by the host-dependent RNA polymerase
  • 2 promoters: 19S (weak) and 35S (strong)
  • P6 translated from monocistronic 19S RNA
  • P6 protein allows ribosomal shunting - associates with RNA and shunts ribosome to next start codon, allowing silent ORFs to be translated
13
Q

Cauliflower mosaic virus replication

A
  • Uses reverse transcription using 35S RNA as a template
  • As it does this it makes more copies of itself
  • Uses rRNA as primers