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Viruses • Individual Viruses = Virion • Not cells – nonliving • Size 0.02 -0.3 μm • Bacterial Viruses = Bacteriophage T4 Viral Genome • Double Strand or Single Strand • DNA or RNA • Most Genomes Linear • Overlapping genes Human Papillomavirus Protein Coat • Capsid, Coat, Shell • Capsomer Individual Proteins • Self Assembly • Nucleocapsid Viral Symmetry • Icosahedral 20 faces, 12 vertices •Helical Icosahedral Subunits Herpes Simplex Virus Tobacco Mosaic Virus Enveloped Virus Complex Virus T 4 Bacteriophage Enzymes in Viruses • Reverse Transcriptase • Lysozyme • RNA Polymerase • Neuraminidase Viral Host • • • • • Living Cells Animal Host Cell Culture Tissue Culture Monolayer Cell Line •Primary Culture Line •Transformation –Viruses –Mutagen •Permanent Cell line •HELA –Henrietta Lacks Quantification of Viruses • Plaque Assay – Bacteria • Efficiency of Plating • Animal Infectivity Methods • End Point Dilution Bacteriophage Plaques Plaques in Tissue Culture Monolayer Viral Replication • Attachment • Penetration Synthesis 1. Production of Early Proteins Replication of Nucleic Acids 2. Production of Late Proteins Viral Coat • Assembly • Release One-step Growth Curve Latent Period •Some Host Cells Use Restriction Enzymes to Destroy DNA Viruses •Some Viruses Can Modify Their Genome’s Restriction Sites for Protection Baltimore Classification Scheme David Baltimore, Howard Temin, Renato Dulbecco 1975 Reverse transciptase Retro virus 6 Classes based on DNA→RNA→Protein 7th Class Hepadnaviruses added +/- SS RNA Viruses DS Intermediates SS DNA Viruses Reverse Transcriptase Virulent Bacteriophage • Lytic T Phages • T4, T7 DS DNA • Head, Tail, Spikes Base Plate, Tail Fibers, Contractile Sheath • Hydroxymethylcytosine Lambda • • • • • • Best Known Virus? Can be Virulent or Temperate Lysis or Lysogeny Becomes Prophage (Provirus) Gives Immunity to Host Specific Insertion Site Maintenance of Lysogeny • Lambda Repressor -Lysogeny • CRO Protein - Lysis • Induction Animal Viruses DNA Viruses RNA Viruses Eukaryotic Host Types of Infections: Lytic Hepatitis A Persistent Latent Herpes Cancer Viruses • Transformation • Neoplasm • Benign • Malignant • Metastasis • Oncogene Retrovirus • • • • • • RNA Genome HIV Reverse Transcriptase DNA Copy Insert into Host Genome AIDS Acquired Immunodeficiency Syndrome HIV – Human Immunodeficiency Virus Subviral Entities • Defective Viruses • Parasitic? • Helper Viruses • Satellite Viruses • AAV – Adenovirus Associated Virus • Specific Insertion Sites Viroids • • • • • • Naked Circles SS RNA 246-375 Nucleotides Plant Diseases Regulatory RNA -sRNA Prions • • • • • • Infectious Proteins? Chaperone Protein Kuru Mad Cow Disease Scrapies CreutzfeldtJakob Disease 5/24/2017 Prion Infectious Cycle • • • • • PrPc → PrPsc Infectious, Sporadic, or Inherited Prion Disease Mice with no PrPc are Normal? Viruses Word List Virion Bacteriophage 28 –200 nm (0.2 μm) Genome SS/DS RNA/DNA Capsid, Coat, Shell Capsomer Self-Assembly Nucleocapsid Viral Symmetry Helical Icosahedral Enveloped Viruses Complex Viruses Enzymes in Virion Reverse Transcriptase Lysozyme Viral Host Living Organisms Cell (Tissue) Culture Monolayer Primary Culture Line Viruses 2 Transformation Permanent Cell Line Quantification of Viruses Plaque Assay Efficiency of Plating Animal Infectivity Methods End Point Dilution Viral Reproduction Attachment Penetration Early Steps (Early Proteins) Replication of Nucleic Acids Synthesis of Proteins (Late) Assembly Release Viruses 3 One-step Growth Curve Latent Period Restriction/ Modification Restriction Enzymes Modification +/- SS RNA Viruses SS DNA Viruses DS Intermediates Reverse Transcriptase BACTERIAL VIRUSES Model Viruses Genetic Engineering RNA Bacteriophage +SS RNA Viruses MS2 “Male” Specific Phage Viruses 4 4 Proteins4 Proteins Maturation, Coat, Lysis & RNA Replicase Overlapping Genes SS DNA Icosahedral Phage ФX 174 DS DNA Phage – Lytic T7, T4 Head, Tail, Base Plate, Spikes, Tail Fibers, Contractile Sheath Hydoxymethylc ytosine Temperate Bacteriophage Lambda Viruses 5 Virulent – Temperate Lysogeny Prophage – Provirus Immunity Lambda Repressor Cro protein Transposable Phage Insertion Elements Transposon Mu Phage – Mutator Animal Viruses Eukaryotic Hosts Lytic Infections Persistent Infections Latent Infections Viruses 6 Cancer Transformation Neoplasm Benign Malignant Metastasis Oncogene +SS RNA Viruses Rhinovirus Foot-andMouth Virus Poliovirus Polyprotein Viral Protease -SS RNA Virus Rhabdovirus RNA Dep. RNA Polymerase Influenza Segmented Genome DS RNA Virus Reovirus Rotavirus Viruses 7 DNA Virus Papovavirus SV 40 Herpesviruses Herpes simplex, Chickenpox, Shingles, Epstein-Barr, Burkitt’s Lymphoma Pox Virus Smallpox Adenovirus Retrovirus Reverse Transcriptase Acquired Immuno deficiency Syndrome – AIDS Viroids SS RNA Circles Viruses 8 Prions “Mad Cow Disease” Kuru Scrapies Creutzfeldt-Jakob Disease
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