34 Questions
What is the size of the diameter of picornaviruses?
~30nm
How many copies of VP4 are present in the mature virion of picornaviruses?
60
What is the function of the internal ribosome entry site (IRES) present in picornavirus RNA?
Allow initiation of translation without having a 5’ cap
What is covalently bound to the 5’ end of picornavirus RNA?
VPg
What is the function of the pyrimidine-rich track located 20-15 nucleotides from AUG in picornavirus RNA?
Facilitate translation at the correct spot
What is the role of VP4 in mature picornavirus virions?
Remains buried within the capsid shell
What is covalently bound to the 5’ end of picornavirus RNA?
Viral protein VPg
What is the function of the internal ribosome entry site (IRES) in picornavirus RNA?
Allow initiation of translation without a 5’ cap
What is the mechanism by which picornavirus infection promotes its own translation in host cells?
Proteolytic cleavage of eIF-4G, abolishing cap-dependent translation
What is the role of VPg in the replication of picornavirus RNAs?
It is covalently bound to uridine residues and serves as a primer for (-) strand synthesis
How are newly synthesized virions released from the host cell?
By lysis
What is the main consequence of picornavirus infection on host cell macromolecular functions?
Shut off host cap-dependent translation and RNA synthesis
What is the role of eukaryotic initiation factors (eIFs) eIF-4A, eIF-4E, and eIF-4G in cellular translation?
They form the eIF-4F complex, bind to 5’ end of mRNA, and recruit a 40S ribosomal subunit
Which cellular process does Picornavirus infection induce in host cells?
Induction of cytoplasmic vesicles
What is the size of the diameter of picornaviruses?
~30nm
What is covalently bound to the 5’ end of picornavirus RNA?
VPg
What is the function of the internal ribosome entry site (IRES) in picornavirus RNA?
Allow initiation of translation without having a 5’ cap
What is the role of VP4 in mature picornavirus virions?
Remains buried within the shell
What is the role of VPg in the replication of picornavirus RNAs?
VPg serves as a primer for (-) strand synthesis
What is the function of the internal ribosome entry site (IRES) present in picornavirus RNA?
It helps with docking of 40S ribosomal subunit
What is covalently bound to the 5’ end of picornavirus RNA?
VPg
What is the main consequence of picornavirus infection on host cell macromolecular functions?
Shut off host cap-dependent translation and RNA synthesis
How are newly synthesized virions released from the host cell?
By lysis
What is the mechanism by which picornavirus infection promotes its own translation in host cells?
Proteolytic cleavage of eIF-4G abolishes cap-dependent translation, promoting viral translation
What is the function of eukaryotic initiation factors (eIFs) eIF-4A, eIF-4E, and eIF-4G in cellular translation?
They form the eIF-4F complex that binds to the 5’ end and recruits a ribosomal subunit.
What is the size of the diameter of picornaviruses?
About 30 nanometers.
What is the role of VP4 in mature picornavirus virions?
VP4 forms a channel in the cell membrane for viral RNA entry into the cytoplasm.
Which cellular process does Picornavirus infection induce in host cells?
Induction of cytoplasmic vesicles.
What is the function of the pyrimidine-rich track located 20-15 nucleotides from AUG in picornavirus RNA?
It acts as an IRES element for cap-independent translation initiation.
What is the main consequence of Picornavirus infection on host cell macromolecular functions?
Shut off host cap-dependent translation and RNA synthesis
What is covalently bound to uridine residues to prime RNA synthesis in Picornavirus replication?
Viral protein, VPg
What is the role of the 40S ribosomal subunit in cellular translation?
Scans mRNA to find the start codon (AUG)
Which cellular process does Picornavirus infection induce in host cells?
Induction of cytoplasmic vesicles
What is the mechanism by which newly synthesized virions are released from the host cell by Picornavirus?
Lysis of the host cell
Study Notes
Picornavirus Structure and Function
- The diameter of picornaviruses is approximately 25-30 nanometers.
- There are 60 copies of VP4 present in the mature virion of picornaviruses.
- The internal ribosome entry site (IRES) present in picornavirus RNA facilitates the translation of viral RNA by allowing the ribosome to bind directly to the RNA, bypassing the need for a cap structure.
- VPg (a protein) is covalently bound to the 5’ end of picornavirus RNA.
Picornavirus Replication and Translation
- The pyrimidine-rich track located 20-15 nucleotides from AUG in picornavirus RNA serves as a binding site for the 40S ribosomal subunit, facilitating translation initiation.
- VP4 plays a crucial role in the formation of mature picornavirus virions.
- VPg is essential for the replication of picornavirus RNAs, as it acts as a primer for RNA synthesis.
- Picornavirus infection promotes its own translation in host cells by inducing the phosphorylation of eIF-4E, which leads to the inhibition of cellular translation and the redirection of the translation machinery to viral RNA.
Host Cell Interactions
- Newly synthesized virions are released from the host cell through the lysis of the cell.
- The main consequence of picornavirus infection on host cell macromolecular functions is the shutoff of cellular translation, allowing the virus to hijack the host cell's translation machinery.
- Picornavirus infection induces autophagy in host cells, which is a cellular process that involves the degradation of cellular components.
- Eukaryotic initiation factors (eIFs) eIF-4A, eIF-4E, and eIF-4G play a crucial role in cellular translation, as they facilitate the initiation of translation.
Test your knowledge of the structure and genome of picornaviruses, including their RNA genome, capsid composition, and binding to cellular receptors.
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