D the Replicative Cycle

Question 1

1. Attachment

Answer 1

capsid surface is uneven, has plateaus and canyons. aa residue lining canyon more conserved than others

Question 2

1. attacment purpose of canyons

Answer 2

bind to host cell receptors called CD155

Question 3

what is CD155

Answer 3

member of ig superfamily. found on epithelial tissues and nervous tissues

Question 4

2. Entry and uncoating

Answer 4

attachment to CD155 causes endocytosis. conformational change in VP1. hydrophobic N terminus of VP1 which is internal in virion becomes exposed on capsid surface. can insert in endosomal membrane forming pore

Question 5

2. entry and uncoating. genome

Answer 5

can exit capsid. released into cytoplasm. called uncoating

Question 6

3. Synthesis of viral protein

Answer 6

VPg is removed from genome, +ive strand RNA is translated as one polyprotein

Question 7

3. syntheis of viral protein

Answer 7

part of it folds up and becomes active protease that cuts polyprotein in 2 places. pieces further cut up by another viral protease

Question 8

3. how does polio can get translated

Answer 8

viral RNA has no cap, 5’ UTR forms series of stem loops which fn as internal ribosome entry site. allows binding of 40S r subunit. process uses C terminal fragment of a host eIF called eIF4G

Question 9

3. inhibition of host translxn

Answer 9

eIF4G is required for 40S r subunit to bind to 5’ cap of host mRNA. viral protease cleaves eIF4G into 2 pieces and host mRNA cannot be translated

Question 10

3. cleaving eIF4G does

Answer 10

inhibition of mRNA host translation and is required for viral mRNA translation

Question 11

4. Evasion of immune system. polio does not require

Answer 11

endomembrane system b/c it is naked therefore does not have spike proteins

Question 12

4. how is MHC presentation of viral peptides to T cells inhibited

Answer 12

viral protein inhibits fusion of transport vesicle from the RER to the golgi apparatus

Question 13

5. where does the virus replicate its genome and mRNA

Answer 13

surface of membrane vesicles

Question 14

6. +ive strand RNA synthesis

Answer 14

used as mRNA and new genome

Question 15

6. newly synthesied VPG, RDRP and +ive strand RNA are associated at

Answer 15

surface of membrane vesicle. +ive strand RNA used as template to make -ive RNA

Question 16

6. primer synthesis

Answer 16

VPg is a 22 aa residue protein. RDRP adds 2 uracil to VPG

Question 17

6. synthesis of -ive RNA aka replicative intermediate RI

Answer 17

primer is transferred to 3’ end of +ive strand RNA H2 bonds to poly-a-tail. RDRP uses 3’ OH of primer to synthesize -ive RNA. binding of primer to polyatail ensures synthesis occurs correct site. 2 strands separate

Question 18

6. +ive strand RNA synthesis

Answer 18

RI used as template. RDRP uses same primer

Question 19

polyatail is virally encoded. dsRNA is separated

Answer 19

-ive RI. + is genome, also VPG removed to make mRNA

Question 20

7. Assembly and maturation

Answer 20

VP0,3,1 form capsid enclosing genome. VP0 cleaved to produce VP4 AND VP2. VP4 interacts w/other capsid components providing stability to virion

Question 21

8. virions are released by

Answer 21

lysis