Virology
	Home | Index | Syllabus | Schedule | Study aids | Computing | Links | Interactive
	Spring, 2004 Lecture Outline 3/18 RETROVIRIDAE Retrovirus intro: large family, getting larger as more discovered retro = backward reverse transcriptase = RNA-directed DNA polymerase- copies RNA into DNA retro-'s differ from all other RNA viruses- can incorporate into host genome only virus family known to simultaneously transform & produce progeny 3 subfamilies: oncoviruses; spumaviruses; lentiviruses human retroviruses: oncoviruses- HTLV-1: helper T-cell leukemia, also fibroblasts HTLV-2, variant of HTLV-1 lentiviruses- HIV structure: Rous sarcoma virus (RSV)- prototype (infects birds) icosahedral; envelope c peplomers; matrix & core RNA: R regions at both ends- repeated seq for dimerization long terminal repeats(LTR) of viral DNA- from U5 (5') & U3 (3') end seq.- important for promotion, enhancement, regulation reverse transcriptase: most prefer Mg++ to Mn++ as cation (one prefers Mn++) carry many molec of pol in virion, instead of on-site translation 3 fxns: complimentary DNA nuclease- digests RNA of DNA/RNA hybrid makes "plus" DNA strand to form dsDNA = provirus some have 4th fxn: integrase- dsDNA ligated into host genome steps after reverse transcription: 1. viral DNA supercoils -> enters nucleus 2. integrates c genome at some site (appears random) 3. host DNA-directed RNA polymerase II transcribes to form viral RNA transcription & translation: LTRs contain: promotors & enhancers; ribosome binding sites; cellular protein binding sites; termination codons; poly(A) signal assembly: 38 S RNA + grp-specific viral proteins -> cell membrane, pick up glycoproteins; during maturation & budding- dimers of 70 S RNA reform defective retroviruses: smaller RNA, half normal size pseudotypes: c simultaneous infection of competent & defective latency: 1. transformation c/out replication; transcription occurs 2. no transcription or replication Viral DNA replication & transformation are mutually exclusive permissive cells vs. nonpermissive cells However, RNA replication and transformation can occur together therefore RNA tumor viruses can reproduce in transformed cells immunological consequences of transformation   Next week: Hepadnaviridae [dsDNA virus] uses reverse transcriptase- see CRC, ch 6 & appropriate parts of Wagner, including ch 21, & on-line Small genome DNA viruses- Microviridae & Inoviridae- see CRC, ch 5 & appropriate parts of Wagner, including ch 17, & on-line
	Home | Index | Syllabus | Schedule | Study aids | Computing | Links | Interactive

 Updated 1/25/04 by thatcher@sonoma.edu