Virology 575: Lecture 4

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Virology 575: Lecture 4
2014-02-05 20:46:08
Virology 575

Virology 575
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  1. Types of viral classification
    Classical system, disease-based classification, Baltimore system
  2. Principal cause of common cold
    Rhinovirus, Family: Picornaviridae, Genus: Enteroviruses
  3. Picornaviridae
    RNA viruses, infect gastrointestinal tract, spread to other areas of body (nervous system)
  4. Virion
    Complete viral particle
  5. Capsid:
    Proteins of the shell, protect genome from damage, is pseudo-stable (needs to be stable outside of the cell and able to release genetic material outside cell). very specific/highly evolved proteins
  6. Many viral capsids have ___
    Repeating patterns, because there is not room for many proteins
  7. Common viral capsid structures
    • Helical: Sheet rolled up
    • Icosahedral: made up of only a few types of proteins, looks like d20 generally
  8. Use of X-ray crystallography in virology
    Visualizing viral proteins
  9. Simple viruses usually have what kind of capsid?
    A simple repetitive one.
  10. Reasons to study DNA viruses
    • Disease (antivirals and vaccines)
    • Vectors for foreign gene expression
    • Models for regulation of gene expression
    • Models for oncogenesis
    • Models for latency
  11. Permissive Host
    an organism/cells that permit completion of a viral multiplication cycle
  12. Non-Permissive Host
    A host that does not permit completion of a viral multiplication cycle. Infection does not occur: host lacks some required factor/anti-viral mechanism
  13. Productive Infection
    Results in production of infectious virus progeny. Infected host may survive
  14. Abortive Infection
    Viral infection is initiated but stalls/is terminated. Host usually survives
  15. Inapparent infection
    Low level infection wherein virus-specific multiplication is difficult to detect and symptoms are absent or inapparent to the host.
  16. Chronic Infection
    Condition in which virus is present and multiplying. The host is a constant source of infectious virus
  17. Latent Infection
    Virus goes dormant but can alternate between periods of active multiplication. Reactivation from latency can result in disease and shedding of infectious virus.
  18. Most human DNA virus can cause:
    Latent infections
  19. How do Small and Large DNA viruses differ in gene expression
    • Small viruses express early genes all at same time and late genes all at same time
    • Large viruses express immediate early genes (regulatory) and delayed early genes (replication) and late genes all at once
  20. How do DNA viruses regulate gene expression
    At a transcriptional level
  21. What do most DNA viruses use to create there proteins?
    Host transcription factors and RNA polymerase
  22. What do DNA viruses use to regulate gene transcription
    Transcriptional activators and repressors
  23. Viral RNAs usually encode ____ proteins
  24. Viral promoters contains binding sites for
    host or viral encoded transcription factors
  25. Viruses can interfere in what part of RNA translation
    • Post-processing: splicing, methylation, poly-adenelation
    • These are all things that viral RNA do not need to do, so this inhibits host protein production but not viral protein production
  26. Families and important examples of small DNA viruses
    • Families: Polyomaviridae, Adenoviridae, Papillomaviridae
    • Examples: SV40, polyomavirus, adenovirus, papilloma virus
  27. Properties of Small DNA viruses
    • use host transcription and DNA synthesis machinery
    • RNA splicing generates multiple virus proteins
    • has capacity to cause tumors
    • causes mild disease in humans
  28. Why do some viruses lead to cancer/tumor
    They need to use host machinery so they force the cell into S phase where it is available.
  29. Why can DNA viruses cause cancer in non-permissive hosts but not permissive hosts
    Some non-permissive hosts can allow the S phase stimulators but not the replication and cell death that would stop permissive host cells from causing uncontrolled growth
  30. SV40, facts:
    • Closed circular dsDNA
    • Encodes 6 proteins: T-antigens and capsid proteins
    • Needs host transcriptional and replication factors
    • Early and late phases
    • Large T antigen controls host cell cycle
  31. SV40 regulation of gene expression
    See Lecture 4
  32. Adenoviruses facts:
    • Intermediate sized DNA virus, linear dsDNA
    • Virion is non-enveloped w/ icosahedral symmetry
    • Acute respiratory infections, conjunctivitis, gastroenteritis
    • Oncogenic (not in humans)
  33. Adenovirus gene expression
    • Expresses: E1A/B/2/3/4 (Early), IX and IVa2 (delayed early), L1/2/3/4/5 (late)
    • All are encoded by splicing and use of overlapping codes
  34. Early Adenovirus genes do what?
    • Viral DNA replication
    • turn-on major late promoter
    • alter splicing and polyadenylation
    • transport viral and cellular RNA
  35. First gene expressed by Adenovirus
    Immediate Early gene (EA1)