Virus Life Cycle 2 Flashcards
According to the lecture, what 3 DNA viruses most commonly cause disease?
Herpesvirus, adenovirus, and papillomavirus
What enzyme do most DNA viruses (except poxvirus) use to transcribe mRNA?
host [DNA-dependent] RNA polymerase
Where in the cell does genome replication occur for most DNA viruses (except poxvirus)?
the nucleus
What enzyme does poxvirus use to transcribe mRNA?
its own, viral [DNA-dependent] RNA polymerase
What kinds of factors do DNA viruses use to regulate transcription of their genome by host RNA polymerase?
Both host and viral transcription factors
Which of the following is not a way that that viruses might manipulate the cellular environment: increase interferon response; advance the cell cycle; inhibit apoptosis; use host transcription factors.
Increase interferon response - interferon is a cytokine that stimulates the immune system against invaders like viruses. A virus wants to decrease (abrogate) interferon response in order to hide out undetected.
What enzyme do parvovirus and papovavirus use to replicate their DNA?
cellular DNA polymerase (small viruses use host DNA pol)
What enzyme do parvovirus and papovavirus use to make mRNA out of their DNA?
cellular RNA polymerase
What enzyme do adenovirus and herpesviruses use to replicate their DNA?
viral DNA polymerase (large viruses encode their own DNA pol; they also encode accessory proteins like thymidine kinase, helicase, primase, etc.)
What enzyme do adenovirus and herpesvirus use to make mRNA out of their DNA?
cellular RNA polymerase
What name is given to the specialized nuclear compartments where viral and cellular proteins accumulate for both viral genome and viral mRNA transcription?
Replication centers
List 3 ways that poxvirus replication differs from most other DNA virus replications.
Uses its own RNA polymerase; replicates DNA in the cytoplasm; assembles virions in the cytoplasm
Where in the cell do adenovirus and herpesvirus assemble their virions? Which virus first builds their capsid shell around a scaffold, then degrades the scaffold to allow DNA entry?
Nucleus; herpesvirus
List the 5 routes of virus egress, 2 using cell associated virions and 3 using virion release into the extracellular space.
Cell associated: cell-to-cell spread, cell fusion/syncytium formation
Release: lysis, budding, exocytosis
Which process allows the virion to take its envelope from the plasma membrane of a cell during egress: budding or exocytosis?
Budding - in exocytosis, the virion is brought in a vesicle to the cell surface, where the vesicle membrane merges with the plasma membrane
What method of egress is used by rotavirus, Norwalk virus, and poliovirus? What feature does this create in a stained lab culture?
Cell lysis (common for GI viruses); virus plaques
What method of egress is employed by measles virus and HIV-1?
Budding
What method of egress is employed by Herpesvirus? What is the source of its viral envelope?
Exocytosis; golgi body
What is formed when glycoprotein-120 on the surface of HIV-1 infected cells mediates the fusion of hundreds of CD4 T-cells? How does this affect the virulence of HIV?
Syncytium; syncytium-inducing strains of HIV are more virulent
What enzyme, targeted by anti-retroviral drug therapy, is responsible for the maturation of HIV-1 particles after budding? Describe 2 changes that it catalyzes.
HIV-1 protease; cleaves Gag into 3 subunits and makes the core trapezoidal
