Smiley-8: Retroviruses and Hepadnaviruses Flashcards
(22 cards)
Are retroviruses enveloped?
yes
Describe genome of retrovirus
ssRNA, +ve sense
How is the retrovirus genome capped and polyadenylated?
coded for by the genome (done by RdRNAP)
Provirus
- dsDNA transcript from +ve sense ssRNA
- integrates to host chromosomes
Where are progeny virions assembled in the host cell?
plasma membrane
How do retroviruses acquire their envelope?
by budding out of host cell
What is inside the retrovirus capsid? (x3)
- 2 identical copies of RNA genome
- RTase
- integrase
Function of integrase
integrate linear dsDNA into host chromosome
What cells do most retroviruses infect effectively?
actively dividing cells
What does an LTR contain?
- RNAPII promoter
- polyadenylation signal
Function of LTR
Directs production of RNA transcripts of integrated provirus using host machinery
What does gag encode?
polyprotein to make viral capsid proteins
What does pol encode?
RTase, RNAse H, and integrase
What does env encode?
envelope proteins
What does pro encode?
protease to cleave polyprotein to make capsid proteins
HIV: What does tat do?
- transcriptional activator
- increase transcription driven from viral LTR
HIV mRNAs are divided into 3:
- unspliced
- singly spliced
- multiply spliced
What do unspliced and multiply spliced HIV mRNAs encode?
structural proteins and viral enzymes packaged into virions
What do multiply spliced mRNAs code?
non-structural regulatory proteins: tat, rev, nef
During early infection of HIV, only ____ mRNAs are made (what type of splicing)?
multiply spliced
Function of rev (x3)
- helps drive infection to late phase to make unspliced and singly spliced transcripts
- suppress further splicing of transcripts to which it is bound
- promotes export from nucleus to cytoplasm
Does RTase have proof-reading ability?
no
