Viral Replication Flashcards
How do you study viral replication
In-vitro
Study of viruses in-vivo is what?
Study of viral pathogenesis
What kind of curve to scientists develop to study viruses
One-step growth curve
In one step growth curve, what does ‘total virus mean’
Input virus (attached and unattached ) and progeny virus (intra- and extracellular)
In one step growth curve, what does ‘total cell free virus’ mean?
Input virus (unattached) and progeny (extracellular)
In one step growth curve, what does ‘total cell-associated virus’ mean?
Input virus (attached, not penetrated) and progeny (intracellular)
For viruses that dont grow in cell cultures, how do you study them?
Use infectious clones
What is the eclipse period
The period after viral penetration and virus releases genome, in which the progeny is not detectable
2-12 hours
T/F the eclipse period is the same as the incubation period
False!
What are some early products from viral replication (3)
- Proteins that shut down cell processes
- Proteins that regulate expression of viral genome
- Enzymes requires for replication of viral nucleic acid
What are some late products of viral replication (1)
Structural proteins
Where does DNA viral replication take place and which enzymes does it use
Nucleus
DdRp (DNA dependent RNA polymerase)
Where does RNA viral replication take place and which enzymes does it use
Cytoplasm
- Retrotranscriptases
- RdRp (RNA viruses)
- DdRp (DNA viruses that replicate in cytoplasm)
What are cellular enzymes for replication (2)
DdDp
DdRp
What are viral enzymes for replication (3)
- Retrotranscripatse
- RdRp
- DdRp
Steps of viral replication
- Attachment
- Penetration (membrane fusion/endocytosis)
- Uncoating
- Transcription/Translation
- Processing
- Assembly/release
How do enveloped viruses penetrate
Membrane fusion
How do naked viruses penetrate
Receptor mediated endocytosis
If DNA viruses un-coat in the cytoplasm, what do they require
Chaperone proteins
Describe ss+ RNA viral transcription/translation
They bind directly to ribosome and start TRANSLATION
Describe ss- RNA viral transcription/translation
Transcription must occur first – cant just fit onto ribosomes
They carry own enzymes (the RdRp protein)
Retroviruses have two copies of ________ and replicate through a _____ intermediate
ss+ RNA
DNA
Which enzyme do retroviruses use? What is the primer?
Reverse transcriptase
tRNA is the primer
Functions of LTR (2)
- Integration to host genome
2. Strong promoter (oncogenic)
Steps of retrovirus replication
- Start with two copies of ss+ RNA
- Reverse transcriptase uses tRNA as a primer
- RNA:DNA hybrid formed
- Copies of ss- DNA form a linear double stranded DNA, containing an LTR at each end
- ds DNA integrates into cellular chromosome as proviral DNA
- Further transcription of viral RNA occurs through proviral DNA
Which viruses undergo translation first (7)
ss+ RNA viruses
CAP-FACT
- Calici
- Astro
- Picorna
- Flavi
- Arteri
- Corona
- Toga
Which viruses undergo transcription first (8)
ss- RNA viruses
ds RNA segmented viruses
RRR- BB- FOAP
- Rhabdo
- Reo
- Retro
- Arena
- Birna
- Bunya
- Orthomyxo
- Paramyxo
- Filo
Which ss+ RNA virus undergoes translation first
Retrovirus
How are naked viruses released post-replication
Accumulate in nucleus/cytoplasm until cell lysis occurs
How are enveloped viruses release post-replication
Exoctyosis
What is a susceptible cell
Virus can enter
What is a permissive cell
Virus can replicate
Which enzyme does poxvirus for reproduction
DdRp - in cytoplasm
