- Attachment
capsid surface is uneven, has plateaus and canyons. aa residue lining canyon more conserved than others
- attacment purpose of canyons
bind to host cell receptors called CD155
what is CD155
member of ig superfamily. found on epithelial tissues and nervous tissues
- Entry and uncoating
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
- entry and uncoating. genome
can exit capsid. released into cytoplasm. called uncoating
- Synthesis of viral protein
VPg is removed from genome, +ive strand RNA is translated as one polyprotein
- syntheis of viral protein
part of it folds up and becomes active protease that cuts polyprotein in 2 places. pieces further cut up by another viral protease
- how does polio can get translated
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
- inhibition of host translxn
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
- cleaving eIF4G does
inhibition of mRNA host translation and is required for viral mRNA translation
- Evasion of immune system. polio does not require
endomembrane system b/c it is naked therefore does not have spike proteins
- how is MHC presentation of viral peptides to T cells inhibited
viral protein inhibits fusion of transport vesicle from the RER to the golgi apparatus
- where does the virus replicate its genome and mRNA
surface of membrane vesicles
- +ive strand RNA synthesis
used as mRNA and new genome
- newly synthesied VPG, RDRP and +ive strand RNA are associated at
surface of membrane vesicle. +ive strand RNA used as template to make -ive RNA
- primer synthesis
VPg is a 22 aa residue protein. RDRP adds 2 uracil to VPG
- synthesis of -ive RNA aka replicative intermediate RI
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
- +ive strand RNA synthesis
RI used as template. RDRP uses same primer
polyatail is virally encoded. dsRNA is separated
-ive RI. + is genome, also VPG removed to make mRNA
- Assembly and maturation
VP0,3,1 form capsid enclosing genome. VP0 cleaved to produce VP4 AND VP2. VP4 interacts w/other capsid components providing stability to virion
- virions are released by
lysis
