CBG Lecture 22: Virus Cell Interactions Flashcards
what morphological effects do viruses have on host cell
effects on nucleus (nuclear inclusion)
inclusion bodies: due to virus factories sometimes remain till cell lysis
cytoskeletal effects
syncytia giant cell formation
what are inclusion bodies
viral replicating factories
what cytoskeletal changes do viruses have on cells
RNA virus is associated with microtubules so changes the cytoskeleton and bends cell into new shapes
what are syncytia
giant cell formaiton -giant multinucleate cell caused by fusion of infected and non infected cell due to viral envelope
which viruses use syncytia
measles and retroviruses
outline main effects viruses have on host cells
- morphological
- biochemical
- genetic
what biochemical effects do viruses have on host cell
- activate cellular protein kinases and transcription factors
activates cell oncogenes, cell cycle arrest
inhibit DNA synthesis
what genetic effects do viruses have on host cell
genralised chromosomal damage
transformation
introduction of oncogenes
give example of induced viral defence
interferon stimualtion of cells which acts to induce a viral state
what does interferon effect the activation of
transcription, translation, protein processing and virus maturation inhibitors
how does interferon block viral activation of transcription inhibitor
by blocking mRNA synthesis
how does interferon block viral activation of translation inhibitor
by blocking mRNA cap methylation, viral RNA function and tRNA
how does interferon block viral activation ofprotein processing inhibior
by blocking protein glycosylation
how does interferon block viral activation of virus maturation inhibiot
by blocking glycoprotein maturation and budding
what is the HIV combination theory
combo of different drugs allowing normal lifespan for HIV sufferes :AZT to inhibit RT, then protease -> attack many stages of lifecycle
give an exmaple of induced effect by TIP
activation of TIP = translation inhibitory protein
how does TIP activation work
interferon binds to outside of cell
TIP produces TIP RNA, translated = TIP protein, bunds to ribosome and modifies it slowing its speed but makes ribosome more careful about the RNA it translates therefore more likely to transfer host RNA and not viral
what is a viral counterdefernce to TIP activation
Influenza has a cap snatching mechanism, it original RNA is capless but takes host cap and puts on its virus therefore host cant get its protein
give an example of a non induced effect against retrovirus
APOBEC3G defends against retroviruses (HIV has overcome this defence by acquisition of vif gene -viral infectivity factor gene)
how has HIV overcome APOBEC
acquired vif gene
how does non induced APOBEC effect work
APOBEC is human antiviral defence eenzyme which catalyses the deamination of C to U in ssDNA on noncoding strand (G -> A on coding strand) this is HYPERMUTATION
how does vif work
vif gene disrupts the antiviral activity of APOBEC by targeting it for ubiquitination
what is base change caused by APOBEC
hypermutation of C to U in ssDNA non coding strand which is G to A hypermutation on coding
despite vif, on what % of viruses does APOBEC work
30%
what is TRIM5
retrovirus restriction factor - uncoats viruses by binding to capsid proteins
what factor inactivates retroviruses by binding to capsid proteins and uncoating
TRIM5
what is RSV
Rous sarcoma Virus - a transforming virus that cn be generated when a cellular protooncogene is captured by insertion into the viral genome during viral replication
how can transforming viruses be generated
when a cellular protooncogene is captured by insertion into the viral genome during viral replication
name a transforming virus
Rous Sarcoma Virus -RSV
what did Peyton Rous do
isolated RSV rous sarcoma virus from a chicken fibrosarcoma
what type of viruses are most oncogene containing viruses
retroviruses
what are viruses related to RSV called
ALVs - dont contain oncogenes
what is src
protein tyrosine kinase -causes ALVs to not be oncogenes
besides encoding src (protein tyrosine kinase) how else can retroviruses transform cells
by altering the expression of cellular oncogenes eg. cellular (c) myc oncogene
give an example of a DNA virus that can cause cell transformation
papillomavirus
what happens if chromosome of papillomavirus remains in an episome - away from host chromosome
get benign growth or wart - not uncontrollable
what happens if theres accidental integration of papillomavirus virus DNa into host chromosome
lead to malignant uncontrollable tumour and cause unrestricted production of viral protein and interfere with p53
name a protooncogene
p53
