Virus/cell interactions 2 Flashcards
What did Peyton Rous do?
took muscle cancer from a chicken,cultured it and ground it up, then injected it in another chicken. Chicken had cancer.This showed virus was responsible
What virus did Peyton Rous isolate,culture and put into a chicken?
RSV-Rous sarcoma virus
define sarcoma
malignant tumor of connective or other nonepithelial tissue.
define fibrosarcoma
a sarcoma in which the predominant cell type is a malignant fibroblast.
how does a transforming virus work? what is the proto oncogene captured by?
when a cellular proto oncogene is captured by insertion into the viral genome during viral replication
what are most oncogene containing viruses?
retroviruses
What is RSV Rous sarcoma virus an example of?
a transforming retrovirus
why is RS Rous sarcoma virus a transforming virus?
it has captured an oncogene that makes sarcoma
what is an oncogene?
a gene that in certain circumstances can transform a cell into a tumor cell
if oncogene badly regulated what does it lead to?
cancer
what is RSV related to?
HIV
what are viruses related to RSV but not containing oncogenes called?
ALVs
explain ALVs wrt replication and cell transformation
virus replication but no transformation of cell
explain RSV wrt replication and cell transformation
virus replication and DOES transform cells
what do ALV and RSV have in common?
both infect chicken cells
what are the 2 ways retroviruses can cause cells to transform?
a) if they contain oncogene they can cause cancer
b) if they alter expression of cellular oncogenes they can also cause cancer
is cellular transformation by DNA viruses always helpful to the virus?
No in fact it is often not helpful
what is an example of a DNA virus that transforms cells?
Papillomavirus
why is the transformation of the papillomavirus bad?
viral proteins are required for controlled replication of the virus (as benign growth/wart) But if the virus is accidentally integrated into the host chromosome this can lead to unbalanced production of viral replication proteins which can lead to a malignant tumour and non production of the whole virus(doesn’t do virus any good)
what does papillomavirus need for controlled replication?
viral proteins
how is the papillomavirus genome organised?
In an episome (chromosome as circular episome)
what is the MMTV?
mouse mammary tumour virus
why are induced defenses not always present?
although they are more specific they are not as efficient for the cell and we only want them when the virus is around
what is an example of a an induced response?
Interferons (IFNs), a group of signaling proteins made and released by host cells in response to the presence of pathogens, such as viruses, bacteria, parasites, or tumor cells. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten their anti-viral defenses.
why is combination therapy good?
targets multiple points of replication cycle in virus, now HIV treatment lasts lifespan
what state do interferons induce?
“viral state”
What things do inteferons activate? (4)
1) transcription inhibitor
2) translation inhibitor
3) protein processing inhibitor
4) virus maturation inhibitor
what is TIP?
translation inhibitory protein`
How does TIP help immune system?
checks CAP on DNA to make ribosome more picky and slower
How has Influenza counteracted TIP?
has cap snatching RNA so steals CAP from host genome and sticks onto virus.
what is are 2 examples of a non induced response?
a) APOBEC35
b) TRIM5
what does APOBEC3G do?
defends against retroviruses by deaminating c–>u this causes HYPERMUTATION therefore the dna synthesized is degraded
What does APOBEC3G cause in the DNA?
HYPERMUTATION as changes c–> u
How a virus overcome APOBEC3G?
HIV has aquired vif
(viral infectivity factor) gene that stopes APOBEC3G
what is VIF?
viral infectivity factor
what is TRIM5 thought to do?
act against uncoating of
viruses by binding to capsid proteins
What does TRIM5 alpha in chimpanzees do and what does this tell us about our past?
Trim5 alpha blocks HIV infections so we could have possibly been able to block HIV infections in the past too if our concestor shared TRIM5alpha
what two examples illustrate viruses overcoming our responses?
Influenza - RNA cap snatching
Vif protein in HIV against APOBEC3G
