Picornaviruses and Their Structure

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Questions and Answers

What is the size of picornaviruses' diameter?

~20nm

~30nm (correct)

~50nm

~40nm

How many copies of VP1, VP2, and VP3 are present in a mature picornavirus virion?

40 copies each

60 copies each (correct)

20 copies each

80 copies each

What is covalently bound to the 5’ end of the picornavirus RNA?

VP4

VPg (correct)

5’ cap

Poly(A) tail

What does the 5’ NCR of picornaviruses contain?

Internal ribosome entry site (IRES) Signup and view all the answers

What is the likely function of the pyrimidine rich track located 20-15 nucleotides from AUG in IRES elements?

To initiate translation at the correct spot Signup and view all the answers

What is the genome type of picornaviruses?

'+' sense ssRNA Signup and view all the answers

What encodes a polyprotein in picornaviruses?

'+' sense ssRNA genome Signup and view all the answers

What remains buried within the capsid shell of a mature picornavirus virion?

VP4 Signup and view all the answers

What allows for translation at an internal site away from the 5’ end in picornaviruses?

Internal ribosome entry site (IRES) Signup and view all the answers

What is the role of eIF-4G in the translation process of picornavirus RNA?

It is proteolytically cleaved by Picornavirus, leading to the abolishment of cap-dependent translation Signup and view all the answers

What is the function of VPg in picornavirus RNA synthesis?

It is covalently bound to uridine residues and serves as a primer for (-) strand synthesis Signup and view all the answers

What is the fate of eIF-4E during Picornavirus infection?

It may be sequestered, leading to a failure in translation initiation Signup and view all the answers

What is the main function of IRES during Picornavirus infection?

To help with docking of 40S ribosomal subunit for cap-independent translation initiation Signup and view all the answers

What happens to eukaryotic initiation factors (eIFs) eIF-4A, eIF-4E, and eIF-4G during Picornavirus infection?

Their functions are disrupted, leading to a shift towards cap-independent translation initiation Signup and view all the answers

What is the consequence of Picornavirus infection on host cell macromolecular functions?

Shut off host cap-dependent translation and RNA synthesis Signup and view all the answers

What is the role of VP0 in virion assembly?

It is cleaved into VP2 and VP4 to form mature virion Signup and view all the answers

What initiates replication of picornavirus RNAs?

A multiprotein complex bound to cellular vesicles Signup and view all the answers

What is the fate of polyprotein P1 in picornaviruses after synthesis?

Cleaved into capsid proteins Signup and view all the answers

What is the main function of pentamers during picornavirus virion assembly?

Self-assemble into provirion along with RNA Signup and view all the answers

Study Notes

Picornavirus Structure

Picornavirus diameter is approximately 25-30 nm.
A mature picornavirus virion contains 60 copies of VP1, VP2, and VP3.

Picornavirus RNA

VPg (Viral Protein genome-linked) is covalently bound to the 5’ end of the picornavirus RNA.
The 5’ NCR (Non-Coding Region) of picornaviruses contains an Internal Ribosome Entry Site (IRES).
The IRES element contains a pyrimidine-rich track located 20-15 nucleotides from the AUG initiation codon, which likely functions as a landing pad for the 40S ribosomal subunit.

Genome and Translation

Picornaviruses have a single-stranded, positive-sense RNA genome.
The genome encodes a polyprotein.
The IRES element allows for translation at an internal site away from the 5’ end.
eIF-4G (Eukaryotic Initiation Factor 4G) is involved in the translation process of picornavirus RNA.

Effects of Infection

During Picornavirus infection, eIF-4G is cleaved, and eIF-4E is phosphorylated.
eIF-4A, eIF-4E, and eIF-4G are inhibited, leading to the shutdown of host cell cap-dependent translation.
The consequence of Picornavirus infection is the inhibition of host cell macromolecular functions.

Virion Assembly

VP0 (Viral Protein 0) is involved in virion assembly.
The main function of pentamers is to facilitate the assembly of the picornavirus virion.
The polyprotein P1 is cleaved into VP0, VP1, and VP3 after synthesis.

Replication

The VPg protein initiates replication of picornavirus RNAs.
The VPg protein is also involved in picornavirus RNA synthesis.

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Description

Test your knowledge about the structure and characteristics of picornaviruses, a group of small RNA genome viruses that infect a variety of hosts including humans, mammals, and birds. Explore their capsid composition, genome, and cellular interaction mechanisms.