Picornaviruses: Structure and Genome
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Questions and Answers

What is the size of the diameter of picornaviruses?

  • ~50nm
  • ~70nm
  • ~30nm (correct)
  • ~20nm

    • How many copies of VP4 are present in the mature virion of picornaviruses?

  • 45
  • 90
  • 60 (correct)
  • 30

    • What is the function of the internal ribosome entry site (IRES) present in picornavirus RNA?

  • Assist in viral assembly
  • Facilitate viral entry into host cells
  • Promote viral replication
  • Allow initiation of translation without having a 5’ cap (correct)

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

    <p>VPg</p> Signup and view all the answers

    What is the function of the pyrimidine-rich track located 20-15 nucleotides from AUG in picornavirus RNA?

    <p>Facilitate translation at the correct spot</p> Signup and view all the answers

    What is the role of VP4 in mature picornavirus virions?

    <p>Remains buried within the capsid shell</p> Signup and view all the answers

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

    <p>Viral protein VPg</p> Signup and view all the answers

    What is the function of the internal ribosome entry site (IRES) in picornavirus RNA?

    <p>Allow initiation of translation without a 5’ cap</p> Signup and view all the answers

    What is the mechanism by which picornavirus infection promotes its own translation in host cells?

    <p>Proteolytic cleavage of eIF-4G, abolishing cap-dependent translation</p> Signup and view all the answers

    What is the role of VPg in the replication of picornavirus RNAs?

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

    How are newly synthesized virions released from the host cell?

    <p>By lysis</p> Signup and view all the answers

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

    <p>Shut off host cap-dependent translation and RNA synthesis</p> Signup and view all the answers

    What is the role of eukaryotic initiation factors (eIFs) eIF-4A, eIF-4E, and eIF-4G in cellular translation?

    <p>They form the eIF-4F complex, bind to 5’ end of mRNA, and recruit a 40S ribosomal subunit</p> Signup and view all the answers

    Which cellular process does Picornavirus infection induce in host cells?

    <p>Induction of cytoplasmic vesicles</p> Signup and view all the answers

    What is the size of the diameter of picornaviruses?

    <p>~30nm</p> Signup and view all the answers

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

    <p>VPg</p> Signup and view all the answers

    What is the function of the internal ribosome entry site (IRES) in picornavirus RNA?

    <p>Allow initiation of translation without having a 5’ cap</p> Signup and view all the answers

    What is the role of VP4 in mature picornavirus virions?

    <p>Remains buried within the shell</p> Signup and view all the answers

    What is the role of VPg in the replication of picornavirus RNAs?

    <p>VPg serves as a primer for (-) strand synthesis</p> Signup and view all the answers

    What is the function of the internal ribosome entry site (IRES) present in picornavirus RNA?

    <p>It helps with docking of 40S ribosomal subunit</p> Signup and view all the answers

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

    <p>VPg</p> Signup and view all the answers

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

    <p>Shut off host cap-dependent translation and RNA synthesis</p> Signup and view all the answers

    How are newly synthesized virions released from the host cell?

    <p>By lysis</p> Signup and view all the answers

    What is the mechanism by which picornavirus infection promotes its own translation in host cells?

    <p>Proteolytic cleavage of eIF-4G abolishes cap-dependent translation, promoting viral translation</p> Signup and view all the answers

    What is the function of eukaryotic initiation factors (eIFs) eIF-4A, eIF-4E, and eIF-4G in cellular translation?

    <p>They form the eIF-4F complex that binds to the 5’ end and recruits a ribosomal subunit.</p> Signup and view all the answers

    What is the size of the diameter of picornaviruses?

    <p>About 30 nanometers.</p> Signup and view all the answers

    What is the role of VP4 in mature picornavirus virions?

    <p>VP4 forms a channel in the cell membrane for viral RNA entry into the cytoplasm.</p> Signup and view all the answers

    Which cellular process does Picornavirus infection induce in host cells?

    <p>Induction of cytoplasmic vesicles.</p> Signup and view all the answers

    What is the function of the pyrimidine-rich track located 20-15 nucleotides from AUG in picornavirus RNA?

    <p>It acts as an IRES element for cap-independent translation initiation.</p> Signup and view all the answers

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

    <p>Shut off host cap-dependent translation and RNA synthesis</p> Signup and view all the answers

    What is covalently bound to uridine residues to prime RNA synthesis in Picornavirus replication?

    <p>Viral protein, VPg</p> Signup and view all the answers

    What is the role of the 40S ribosomal subunit in cellular translation?

    <p>Scans mRNA to find the start codon (AUG)</p> Signup and view all the answers

    Which cellular process does Picornavirus infection induce in host cells?

    <p>Induction of cytoplasmic vesicles</p> Signup and view all the answers

    What is the mechanism by which newly synthesized virions are released from the host cell by Picornavirus?

    <p>Lysis of the host cell</p> Signup and view all the answers

    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.

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    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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