Virus Life Cycle 1 Flashcards
What term refers to the interactions between viruses and specific species or tissues before binding occurs?
Recognition
What term refers to the entry of a virus particle (virion) into a cell?
Penetration
What term refers to the binding of a viral surface molecule to its specific cellular receptor?
Attachment
What term refers to the species that a virus preferentially infects?
Host range
What term refers to the preferred cell type that a virus infects?
Tissue tropism
What term describes a cell that can support virus replication and virion synthesis?
Permissive
What term describes a cell that a virus can enter?
Susceptible
Describe the attachment and penetration of rotavirus into a host cell.
Attachment: capsid to cell membrane (rotavirus is non-enveloped)
Penetration: endocytosis + endosome lysis
Give the host range, recognition tissue, and tissue tropism for rotavirus.
Host range: humans, some mammals and birds
Recognition: GI mucosa
Tropism: enterocytes
Describe the attachment and penetration of Epstein-Barr Virus into a host cell.
Attachment: envelope to ECM & cell membrane (EBV is enveloped)
Penetration: fusion of envelope to plasma membrane + uncoating at the nuclear pore
Give the host range, recognition tissue, and tissue tropism for Epstein-Barr Virus.
Host range: humans only (Herpesviruses and HIV are humans-only)
Recognition: oral mucosa
Tropism: epithelial cells and B cells
A certain naked virion attaches to a membrane receptor and forms a pore in the plasma membrane. Uncoating occurs through the pore, either at the plasma membrane or within an endosome. What virus from lecture is being described?
Poliovirus
What cells are susceptible and/or permissive for HIV?
Only human CD4 T cells are susceptible, although all T cells would be permissive if the virus could enter. (Also macrophages can become susceptible and permissive as the virus grows and mutates)
What term describe the release of the viral genome into a cell?
Uncoating
List 3 common mechanisms for virus uncoating.
- Uncoating at the plasma membrane
- Uncoating within endosomes
- Uncoating at the nuclear membrane
What enzymes do RNA viruses, DNA viruses, and Retroviruses use to make mRNA?
RNA viruses use RDRP (RNA-dependent RNA Polymerase); DNA viruses and Retroviruses use host RNA Polymerase II
Which strand of RNA is used to make proteins: the (+) or (-) strand? What does the other strand do?
The positive/sense/mRNA strand encodes for proteins. The negative strand can be used to make more (+) strands or packaged into a virion
List up to 4 factors that contribute to the high mutation rate of RNA viruses.
High processivity/efficiency of RDRP, low fidelity of RDRP, high recombination rates, high reassortment of gene segments
Describe where in a cell RDRP is usually found. How does it move during RNA transcription?
In the cytoplasm, but attached to a cell membrane - it stays stationary while the RNA moves through
FIll in the blanks. In a RNA virus, RNA is both ____________ and _____________.
the genetic material; the mRNA / template for protein synthesis
What molecules in an RNA virus can make proteins out of the RNA templates?
Host ribosomes
Just for clarity’s sake, what exactly does RDRP do anyways? Does it: synthesize (+)RNA from (-)RNA, synthesize (-)RNA from (+)RNA, synthesize mRNA from (+)RNA, and/or synthesize proteins from mRNA?
Only the first 2 choices. RDRP just copies RNA, it doesn’t synthesize proteins (that’s a ribosome’s job). Also mRNA is synthesized from (-)RNA.
Name the main RNA virus whose RDRP functions in the nucleus instead of in the cytoplasm. What molecule carries the RDRP into the nucleus?
Influenza; nucleoprotein (NP) carries it
If the mutation rate of E. coli RNA polymerase is about 1 error in 10^6 nucleotides, what is the approximate error rate of RDRP?
About 1 in 10^3-10^4
