Biology 331 Virology I Recall - non-cellular, obligate intracellular parasites

Some History Beijerinck, Tobacco Mosaic Virus - filter Baltimore, first retrovirus Electron microscopy and X-ray crystallography (mid-1900’s) required to actually see viruses.

All Viruses Contain Genetic Material DNA or - single or double stranded (ss, ds) ss(+) = coding, ribosome can translate ss(-) = non-coding, complement (+) made first Form determines replication strategy

Baltimore Classification System Class I - ds DNA genomes Class IV - ss (+) RNA genome Class V - ss (-) RNA genome Class VI - ss (+) RNA with DNA intermediate Class VII - ds DNA with RNA intermediate We will not be covering Class II/III

All Viruses Contain Proteins Capsid icosahedron shells hold DNA/RNA, Nucleocapsid directly wraps DNA/RNA, helical Some have structural tails, functional enzymes But - truism of virology - NONE has ribosomes

Some Viruses Steal/Contain Envelopes Host membrane, studded with viral proteins Make less hardy outside host, transmission

Virus Replication - Common Features Attachment - surface protein + host receptor Penetration - receptor-mediated entry of capsid Synthesis - new proteins and genetic material Assembly - packaging of viruses Release - exit of mature viruses from cell Cells infected = host range; some acute, latent, chronic, oncogenic…

Class I Viruses Virulent T4 Phage Replication always lyses host, Escherichia Unenveloped capsid + tail attaches to LPS Induces contraction - DNA injected Transcription and translation by host machinery

Temperate Lambda Phage Temperate - lysis or lysogeny of Escherichia Lysogeny - replication without lysis Structure, attachment, penetration like T4 Early genes: ASSESS HOST HEALTH… BAD: late gene expressed, inducing lysis GOOD: DNA integrates, host passively copies

Transduction Phage transfer of bacterial DNA between hosts Generalized: accidental packaging during lysis Specialized: recombinant viruses after lysogeny

Papillomavirus For this course, Polyomavirus = Papillomavirus Small, unenveloped, capsid, 65+ strains DNA + stolen histones, less than 10 genes All central dogma steps carried out by host

Transformation If host cells not dividing, papilloma activates CIS = integrating DNA turns on adjacent genes TRANS = protein/T-Ag turns on distant genes RESULT - benign warts, cervical cancer (4/65) Pap tests, surgery, vaccine… condoms ???

Variola/Smallpox 2 envelopes, nucleocapsid/genome genes Viral DNA & RNA Pol enzymes carried in virus Host ribosomes translate - ALL in cytoplasm Exit via Golgi AND cell membrane