CBG Lecture 21: Viral Replication

Question 1

what are MAIN steps of viral replicaiton

Answer 1

infection and disassembly of infectious virus particle
replication viral genome
synthesis viral proteins using host cell machinery
reassembly into progeny virus particles

Question 2

what is eclipse phase

Answer 2

basically see no virus: virus starts to build up proteins and switch to replication

Question 3

what is phase called where you “see” no virus, but virus is building up and using host cells machinery to swtich to replication

Answer 3

eclipse phase (think lag)

Question 4

what is maturation and release phase

Answer 4

virus matures morphologically and can occur outside of cell

Question 5

what is the phase where the virus matures morphologically

Answer 5

maturation and release phase

Question 6

what is cell/tissue tropism

Answer 6

where different viruses recognise different cell receptors on cell surface - determining which cells get infected

Question 7

what type of viral receptors are there

Answer 7

integrins for DNA viruses
CD21 fir estein barr virus
CD4 for HIV1/2
Glycoproteins
Ach receptor for rabies

Question 8

which receptor does rabies use

Answer 8

ACh

Question 9

which receptor does HIV use

Answer 9

CD4

Question 10

which receptor does epstein barr use

Answer 10

CD21

Question 11

which receptor does adenovirus use

Answer 11

integrins

Question 12

how does HIV show cellular tropisms

Answer 12

mutations allow switching between cell targets as HIV can attach to either alpha or beta chemokine receptro

Question 13

which receptor can HIV attach to

Answer 13

CD4 with alphaa OR beta chemokine receptor

Question 14

which virus attaches to CD4 with alpha or beta chemokine receptor

Answer 14

HIV

Question 15

what are common mechanisms used by viruses to infect a host cell as a prelude to viral replication

Answer 15

fusion or endocytosis

uncoating = disassembly

Question 16

how does HIV undergo infection and disassembly

Answer 16

fusion then uncoating, leave env proteins on membrane

Question 17

how does influenz undergo infection and disassembly

Answer 17

endocytosed, then fusion and uncoating within an endosome as it becomes acidified

Question 18

how does polio undergo infection and disassembly

Answer 18

endocytosed then uncoating

Question 19

which virus undergoes fusion then uncoating, leave env proteins on membrane

Answer 19

HIV

Question 20

which virus undergoes endocytosed, then fusion and uncoating within an endosome

Answer 20

influenz

Question 21

how do non envelope proteins enter host cell

Answer 21

capsid binds to cell receptor as no env proteins
cant fuse cos no lipid membrane
endocytosis
conformational change
extruded RNA

Question 22

why cant non env proteins fuse with cell membrane

Answer 22

they have no env proteins

Question 23

where do RNA viruses tend to end up

Answer 23

in cytoplasm

Question 24

where do most DNA viruses replicate

Answer 24

in nucleus

Question 25

which dna virus doesnt replicate in nucleus

Answer 25

poxvirus

Question 26

which rna virus doesnt replicate in cytoplasm

Answer 26

retrovirus

Question 27

which viral rna genome is equivalent to mRNA and can therefore have direct translation

Answer 27

ssRNA+

Question 28

what is ssRNA+ the same as

Answer 28

mRNA

Question 29

how does ssRNA+ viruses replicate

Answer 29

genome is mRNA so can translate dirctly | uses cells RNa dep. RNAP to turn from +sense to -sense so that product is +sense

Question 30

how does ssRNA- virus replicate

Answer 30

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

Question 31

how is dsDNA virus replicated

Answer 31

normal transcription in nucleus using cells DNAP

Question 32

why doesnt poxvirus need nucleus to replicate

Answer 32

becuase they carry a transcription mechanism

Question 33

how do retroviruses replicate

Answer 33

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

Question 34

where does capsid assembly normally happen

Answer 34

@ site of viral genome replication- often self assembly with simultaneous binding of viral genome to capsid rpoteins

Question 35

where are viruses with envelopes usually assembled

Answer 35

either on surgace of cell or in sub cellular compartment

Question 36

where is viral membrane derived from

Answer 36

the host cell

Question 37

what two types of assembly of viruses are there

Answer 37

subsurface-smallpox | surface- retroviruses

Question 38

outline the lifecycle of HIV1

Answer 38

``` 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 ```

Question 39

what are the main domains of HIV1 genome

Answer 39

gag- make capsid pol - non structural:replicative function proteins:RT/protease/integrase env=envelope

Question 40

what does pol domain do

Answer 40

make non structural proteins eg.enzymes: RT protease integrase

Question 41

what is vpr gene on Retroviruses

Answer 41

counteract defence protein+immune system of host cell - budding

Question 42

which gene involved in counteractng immune system and budding of HIV

Answer 42

vpr

Question 43

which genes regulate expression of HIV

Answer 43

tat and rev

Question 44

which gene is a cell cycle arrest in HIV

Answer 44

vpu

Question 45

what is vif gene

Answer 45

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

Question 46

what gene counteracts hypermutation by host cell

Answer 46

vif stops host hypermutating