CBG Lecture 21: Viral Replication Flashcards
what are MAIN steps of viral replicaiton
infection and disassembly of infectious virus particle
replication viral genome
synthesis viral proteins using host cell machinery
reassembly into progeny virus particles
what is eclipse phase
basically see no virus: virus starts to build up proteins and switch to replication
what is phase called where you “see” no virus, but virus is building up and using host cells machinery to swtich to replication
eclipse phase (think lag)
what is maturation and release phase
virus matures morphologically and can occur outside of cell
what is the phase where the virus matures morphologically
maturation and release phase
what is cell/tissue tropism
where different viruses recognise different cell receptors on cell surface - determining which cells get infected
what type of viral receptors are there
integrins for DNA viruses CD21 fir estein barr virus CD4 for HIV1/2 Glycoproteins Ach receptor for rabies
which receptor does rabies use
ACh
which receptor does HIV use
CD4
which receptor does epstein barr use
CD21
which receptor does adenovirus use
integrins
how does HIV show cellular tropisms
mutations allow switching between cell targets as HIV can attach to either alpha or beta chemokine receptro
which receptor can HIV attach to
CD4 with alphaa OR beta chemokine receptor
which virus attaches to CD4 with alpha or beta chemokine receptor
HIV
what are common mechanisms used by viruses to infect a host cell as a prelude to viral replication
fusion or endocytosis
uncoating = disassembly
how does HIV undergo infection and disassembly
fusion then uncoating, leave env proteins on membrane
how does influenz undergo infection and disassembly
endocytosed, then fusion and uncoating within an endosome as it becomes acidified
how does polio undergo infection and disassembly
endocytosed then uncoating
which virus undergoes fusion then uncoating, leave env proteins on membrane
HIV
which virus undergoes endocytosed, then fusion and uncoating within an endosome
influenz
how do non envelope proteins enter host cell
capsid binds to cell receptor as no env proteins cant fuse cos no lipid membrane endocytosis conformational change extruded RNA
why cant non env proteins fuse with cell membrane
they have no env proteins
where do RNA viruses tend to end up
in cytoplasm
where do most DNA viruses replicate
in nucleus
which dna virus doesnt replicate in nucleus
poxvirus
which rna virus doesnt replicate in cytoplasm
retrovirus
which viral rna genome is equivalent to mRNA and can therefore have direct translation
ssRNA+
what is ssRNA+ the same as
mRNA
how does ssRNA+ viruses replicate
genome is mRNA so can translate dirctly
uses cells RNa dep. RNAP to turn from +sense to -sense so that product is +sense
how does ssRNA- virus replicate
its antisense to mRNA so RNA dep RNAP mst be carried to synthesis mRNA
cant translate directly so needs viral polymerase to transfer to +sense then translate
how is dsDNA virus replicated
normal transcription in nucleus using cells DNAP
why doesnt poxvirus need nucleus to replicate
becuase they carry a transcription mechanism
how do retroviruses replicate
they carry a RT to make DNA out of the RNA
use their RT to made dsDNA out of their RNA, then integrate the dsDNA into chromosome
where does capsid assembly normally happen
@ site of viral genome replication- often self assembly with simultaneous binding of viral genome to capsid rpoteins
where are viruses with envelopes usually assembled
either on surgace of cell or in sub cellular compartment
where is viral membrane derived from
the host cell
what two types of assembly of viruses are there
subsurface-smallpox
surface- retroviruses
outline the lifecycle of HIV1
entry into cell loss envelope RT makes DNA/RN then DNAds integration of DNA copy into host transcription translation of capsid protein,env protein and RT then spontaneous assembly
what are the main domains of HIV1 genome
gag- make capsid
pol - non structural:replicative function proteins:RT/protease/integrase
env=envelope
what does pol domain do
make non structural proteins eg.enzymes: RT protease integrase
what is vpr gene on Retroviruses
counteract defence protein+immune system of host cell - budding
which gene involved in counteractng immune system and budding of HIV
vpr
which genes regulate expression of HIV
tat and rev
which gene is a cell cycle arrest in HIV
vpu
what is vif gene
in absence of vif, a virus is hypermutated (G to A in DNA sequence) caused by host defence protein
vif is virus counter defence protein for hypermutation and prevents tetherin stopping viruses
what gene counteracts hypermutation by host cell
vif stops host hypermutating
