Viruses in Action Flashcards
What is the site of most DNA virus replication?
Nucleus
What is the site of most RNA virus replication?
Cytoplasm
Compare what RNA viruses vs DNA viruses need to replicate
All RNA viruses need RNA-dependent RNA polymerases to replicate their genomes, as their host cells do not have the necessary enzymes for transcription.
DNA viruses typically use the host cell’s DNA dependent RNA polymerases for transcription (although some DNA viruses encode their own)
Compare Cap vs No Cap viruses
Cap: Some viruses (e.g. Influenza) use a “cap-snatching” mechanism to steal the 5’ cap from host mRNAs, which helps in the stability and translation of viral mRNA, as it is recognised by ribosomes
No Cap: Other viruses (e.g. Poliovirus) do not have a 5’ cap. Instead they use an internal ribosome entry site (IRES) to initiate translation
PolA tail viruses
Many viruses (e.g. HIV) add a polyA tail to their mRNA, which helps stabilise the mRNA and aids in translation
Virus priming vs no priming
Some viruses (e.g. Poliovirus) use a protein primer VPg to initiate RNA synthesis
Other viruses use short internal RNA olives that can be used as primers (e.g. Bunyaviruses)
Other viruses are primer independent
What is a cap and what is its function?
Methylated guanine nucleotide
Protects from 5’ - 3’ degradation, and is recognised by ribosomes
What is a polyA tail and what is its function?
PolyA polymerase adds 100-200 AAAAs
Protects from 3’ - 5’ degradation
What is viral RNA synthesis initiated by?
RNA dependent RNA polymerase
How does HSV-1 exploit cell machinery?
Encodes proteins to actively destroy mRNAs
Polyadenylate-binding protein is recruited to HSV mRNAs via ICP 27; allows viral mRNAs to get out of nucleus
Baltimore of Influenza A
Enveloped ssRNA (+ sense)
