CSB351Y1 Lecture Notes - Lecture 11: Polio Vaccine, Dna Virus, Baltimore Classification
Lecture 11: DNA Virus Replication
The Baltimore Classification System
dsDNA Replication
• Model of DNA replication in eukaryotic cells
• Packaging of dsDNA into nucleosomes
• Circular dsDNA virus replication
• Linear dsDNA virus replication
Origin of Replication (ori)
Proteins involved in DNA Replication
Cellular replication Summary
Packaging of DNA into nucleosomes
Events in dsDNA virus Replication
1. Attachment and entry of virus into cells
- Viral DNA entry into the nucleus
2. Primary (early) transcription by host enzymes (mRNAs)
3. Translation (ribosomes) of early proteins
4. Viral genomic DNA replication (nucleus)
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5. Late transcription (nucleus)
6. Synthesis of (late structural) protein (cytosol)
7. Assembly into virions
dsDNA Virus Replication
• Circular dsDNA viruses
- SV40 polyomavirus (5.3 kb) – poly (many) oma (tumor)
- Papillomavirus (8 kb) – papilla (nipple, wart) oma (tumor)
- Baculovirus (100-180 kb) – baculum (stick, shape of virion)
• Linear dsDNA viruses
- Adenovirus (30-36 kb) – adeno (gland, site of first isolation, adenoids)
- Herpes Simplex Virus (125-250 kb) – herpein (creep, fast spreading)
- Poxvirus (1500259 kb) – pox/pocks (blistering skin lesion)
Distinctive Characteristics of Polyomaviruses
• Simian virus 40 was found as a contaminant of Salk polio vaccine
- Administered to millions of people
• Human polyomaviruses are widespread but cause disease only rarely
- Progressive multifocal leukoencephalopathy (PML) is caused by JC virus in immunocompromised individuals
(rare demyelinating disease)
◼ Mouse polyomavirus, simian virus 30
◼ Polyomaviruses infecting birds, rodents, cattle
◼ Two human viruses – BK and JC virus
Simian Virus 40 (SV40)
• Small DNA tumor virus
• 5243 bp circular dsDNA
• Member of polyomaviruses
• Cotais a ii hroosoe
SV40 Replication
1. Primary (early) transcription by host enzymes (cellular RNA polymerase II)
2. Translation of early (regulatory) proteins
3. Viral genomic DNA replication
4. Late transcription
5. Synthesis of late (structural) protein
6. Assembly into virions
Genome of Polyomavirus
• Components of polyomavirus virion
• Gymnastics of circular DNA molecules
Map of Mouse Polyomavirus Genome
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