RNA Virus Replication/Picornaviruses Flashcards
What is the capsid structure, and nucleic acid type of Picornaviridae?
Capsid - icosahedral, four structural proteins VP1-4
NA - Single stranded, nonsegmented RNA
What is the polarity of the genome of Picornaviridae and why is this significant?
+ polarity genome - means it can act as mRNA
Genome can transfect cells and initiate infection
Describe Picornaviridae attachment.
Attaches to cell receptor (PVR or CD155)
Loses VP-4 protein from capsid
Penetrates via viropexis
Where does uncoating occur for Picornaviridae?
Cytoplasm
Loses VP1-3
What occurs after uncoating?
The viral genome can be translated into viral proteins via cellular ribosomal subunits
What is IRES?
Internal Ribosome Entry Site
Specialized structure on the 5’ end of the viral mRNA that consists of about 700 ribonucleotides and is essential for viral mRNA translation
What is viral mRNA translated into?
Polyproteins
How does poliovirus infection affect cellular ribosomes?
Causes disruption of pre-existing polyribosomes to make ribosomes available for viral replication
What is polyprotein P123?
Translational product of +RNA w/o VPg
Precursor protein
What are the products of P123?
P1 - Capsid proteins VP1-4
P2 - proteases
P3 - VPg and 3D (polymerase + host factor Hf)
What is viral protein 3D?
RNA dependent-RNA polymerase which combines with hostfactor (Hf)
What is the difference between +RNA with VPg and w/o VPg?
+RNA w/ VPg = RNA for replication
+RNA w/o VPg = mRNA that is translated (e.g. into P123)
How is viral RNA replicated?
RNA polymerase and genomic RNA with VPg is involved in replication
Replication intermediates are formed by +RNA being converted to many -RNAs
Full length -RNAs are copied into + genomic RNAs
