Topic 7: The Biology of Replication of Viruses
Transcription and RNA processing
- What is transcription? What are the generic steps in this process? What happens to RNA transcripts?
- What are the different possible fates of viral mRNAs? What are the steps in the transcription of pre-‐mRNA? Which control elements regulate mRNA synthesis?
- What are the steps in the initiation of mRNA synthesis? How does an enhancer work?
- Host or viral proteins may regulate transcription. How do they function? Describe positive autoregulatory and cascade regulation.
- What is a transcriptional cascade and why is it necessary?
Reverse transcription and integration
- Explain the statement, “retroviral genomes never replicate”.
- What are the unique viral enzymes required to make more retroviral genomes? What do they do? What is the origin of the name of the enzyme?
- What does this statement mean: Retroviral genomes are diploid? What good is this property?
- What is a provirus?
- Understand how reverse transcription works: what are the primers for the polymerase? Why are there several ‘jumps’ on the template?
- What are the functions of RNAse H and integrase during retroviral replication?
- Which enzyme produces viral mRNAs in a cell infected with a retrovirus? Where is the promoter for mRNA synthesis?
- Both hepadnaviruses and retroviruses use reverse transcriptase to replicate, yet the retroviral virion has a (+) ssRNA inside while the hepadnaviral virion has a gapped dsDNA molecule inside. What’s that all about?
- Doe the hepadnavirus genome encode an RNAse H? An integrase? Why or why not? Half of your DNA is made of mobile genetic elements. How did they get there?
- What is the function of the 5’-‐cap on mRNAs?
- How is the translation from an IRES different from a cap‐dependent translation?
- Does poliovirus require cap-‐dependent translation for expression of its viral gene products? Does initiation of translation always begin with a methionine?
- How do viruses get around the ‘one mRNA, one protein’ limitation of the eukaryotic translation apparatus?
- What is an eIF2α kinase and what does it do? How do viruses get around it?
- How does cleavage of eIF4G interfere with translation? Why does this occur in virus-‐ infected cells?
- Explain the statement that the virion assembly process is irreversible during assembly but reversible during entry.
- Why must viral proteins achieve high concentrations in the cell? How is this achieved? How do viral structural proteins go to the ‘right place’ in the cell?
- What features or motifs are found on integral membrane proteins that are necessary for them to function in the plasma membrane?
- What is a sub-assembly? Provide an example.
- Distinguish between assisted assembly and self‐assembly.
- We distinguished between sequential and concerted assembly. How do these processes differ?
- How does the viral nucleic acid get packaged into a virion? How is the viral genome distinguished from other nucleic acids in the cell?
- The egress of a retrovirus and a herpesvirus are remarkably different even though they both are enveloped viruses. Where does the envelope for each virus originate?
- How does an L domain participate in viral budding?
Credit: Prof. V. Racaniello