CSB351Y1 Lecture Notes - Lecture 13: Hepatitis B Virus, Cauliflower Mosaic Virus, Hepadnaviridae
26 May 2018
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Lecture 13: Pararetrovirus – Cauliflower Mosaic Virus (CaMV)
• Two major groups
1. Caulimovirus (plants)
2. Hepadnavirus (human and animals)
Replication of Caulimovirus CamV
• Viruses using reverse transcriptase to replicate an RNA precursor into dsDNA
• Large majority of plant viruses are RNA viruses
• Only two groups of plant viruses have DNA – caulimoviruses (CaMV) and Geminivirus (BGMV)
Pararetrovirus
1. Plant caulimovirus (CaMV) and Plant Badnavirus – Banana Streak Virus (BSB)
2. Animal Hepadnavirus – Hepatitis B Virus (HBV)
1. Caulimovirus
• Group of plant viruses with dsDNA circular genome
• Prototype is cauliflower mosaic virus (CaMV)
• Structure – non-enveloped, large (50nm) diameter) icosahedral particles
composed of 420 subunits (T=7)
- Virion shell is multi-layered
• Contains about 8kb dsDNA genome
CaMV Genome
• In infected cytoplasm, CaMV is pre-genomic RNA with 180 nucleotide redundancy and as replicative
intermediate forms
• In virus particles, CaMV is open circular dsDNA
- Open form is due to nicks at specific sites in both strands with short overhangs, remnant of reverse
transcription process, which are apparently removed in infected nucleus
• In infected plant nuclei, CaMV is supercoiled DNA bound to nucleosomes (mini-chromosome)
- Gaps have been repaired
• There are limits to the use of CaMV as a vector for foreign gene expression
- Infections are systemic and even its DNA is infectious when inoculated on abraded plant surfaces
- Host range is quite limited
- CaMV genomes exceeding natural genome size (8024bp) by even a few hundred bp are not packaged into
virions
• 3 discontinuities (one break in (+) strand and two brakes in (-) strand)
• At the positios of these disotiuities, 5’ ad 3’ eds of iteupted stads oelap eah othe
• ORF I – movement protein
• ORF II – insect transmission factor
• ORF III – DNA binding protein
• ORF IV – capsid protein
• ORF V – Protease, reverse transcriptase and RNaseH
• ORF VI – translational activator/ inclusion body protein
• ORF VII – unknown (dispensable)
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Document Summary
Lecture 13: pararetrovirus cauliflower mosaic virus (camv: two major groups, caulimovirus (plants, hepadnavirus (human and animals) Replication of caulimovirus camv: viruses using reverse transcriptase to replicate an rna precursor into dsdna, only two groups of plant viruses have dna caulimoviruses (camv) and geminivirus (bgmv) Large majority of plant viruses are rna viruses. Virion shell is multi-layered: contains about 8kb dsdna genome. In infected cytoplasm, camv is pre-genomic rna with 180 nucleotide redundancy and as replicative intermediate forms. In virus particles, camv is open circular dsdna. Open form is due to nicks at specific sites in both strands with short overhangs, remnant of reverse transcription process, which are apparently removed in infected nucleus. In infected plant nuclei, camv is supercoiled dna bound to nucleosomes (mini-chromosome) Gaps have been repaired: there are limits to the use of camv as a vector for foreign gene expression. Infections are systemic and even its dna is infectious when inoculated on abraded plant surfaces.
