83 Questions
Which segment of the influenza virus genome encodes for three RNA polymerase subunits?
Segment 6
What is the total size range of the influenza virus genome?
$10-15$ kb
Which viral particles package nine out of the eleven different viral proteins?
Viral particles from segments 1-6
What do Uni-12 and Uni-13 represent in the context of influenza virus genome?
Highly conserved sequences
What is the diameter of naked icosahedral capsid of Picornaviruses?
30nm
How many copies of VP4 are present in a mature Picornavirus virion?
20 copies
What is covalently bound to the 5’ end of the RNA in Picornaviruses?
$VPg$
What type of RNA genome do Picornaviruses possess?
- sense ssRNA
Which cellular receptor does Filovirus GP bind to for attachment and entry?
Asialoglycoprotein receptor
How is the Ebola virus released from cells?
Budding
What is the function of sGP released from infected cells?
Serves as a biomarker and vaccine/antiviral target
Which protein mediates the attachment and entry of the Ebola virus?
GP
What triggers the fusion of the Ebola virus within vesicles?
Low pH
Which protein is associated with the viral envelope and facilitates viral particles' formation and release?
$ ext{VP40}$
What is the potential function of sGP in Ebola virus infection?
Structural protein by forming a complex with GP2 and limiting GP cytotoxicity
Which family does the Ebola virus belong to?
Orthomyxoviridae
What are some symptoms of Orthomyxoviridae infections?
High fever, sore throat, cough, headache, muscular pain
What is a potential concern for survivors of Ebola virus infection?
Latent infection and periodic spikes in EBOV antibodies
Apart from Ebola virus, which other genera are included in the family Orthomyxoviridae?
Thogotovirus and Isavirus
What is the unique protein found in Filoviruses?
P4
How are structural proteins generated in Filoviruses?
Post-translationally
Where are Capsid proteins palmitoylated in Filoviruses?
Golgi
What is the genome size of Marburg virus?
$15-19$kb
What is the result of Ebola virus outbreaks?
$90 ext{%}$ mortality rate
How many genera of filoviruses exist?
Two: Marburgvirus and Ebolavirus
How are Filovirus infections among humans primarily transmitted?
Physical contact with secretions/excretions
Where does replication occur for Ebola virus?
Cytoplasm
What is unique about Ebola virus genome compared to Marburg virus genome?
Ebola virus genome has mRNA editing while Marburg virus does not
What process does Ebola virus use to produce two glycoproteins from the same gene?
mRNA editing
Which mechanism allows translation initiation without a 5’ cap?
Internal ribosome entry site (IRES)
What is the consequence of Picornavirus infection on host cell translation?
Abolishing cap-dependent translation
What aids in the docking of the 40S ribosomal subunit and initiating protein translation?
Host cell proteins binding to IRES
How are viral proteins initially made?
As a single precursor polyprotein autocatalytically cleaved by viral proteinases
Where is viral RNA replication initiated?
In a multi-protein complex bound to cellular vesicles
What is involved in the entry of poliovirus RNA into the cytoplasm?
Major rearrangements leading to the formation of a channel in the cell membrane
What is involved in Flavivirus virion assembly?
Cleavage of VP0 to VP2 plus VP4, with self-assembling protomers into pentamers.
What are the consequences of Picornavirus infection?
Inhibits host cell cap-dependent translation and RNA synthesis, induces cytoplasmic vesicles, and alters intracellular transport pathways.
What does Flavivirus virion contain?
An envelope with envelope proteins arranged with icosahedral symmetry.
How does Flavivirus genome organization compare to Togaviruses?
Most resembles that of Picornaviruses and is distinct from Togaviruses despite similar virion morphology and transmission via arthropods.
Which protein of flaviviruses is a type I membrane protein found as a dimer?
E protein
How do flaviviruses enter cells?
Endocytosis within clathrin-coated vesicles
What is the role of the precursor membrane protein (prM) in flaviviruses?
Forms a heterodimer with the E protein in the endoplasmic reticulum
How do togaviruses cause disease transmission in animals and humans?
Through mosquitoes
What is the genome type of togaviruses?
Single-stranded RNA
What is the role of the E glycoprotein of togaviruses?
Binds to cellular receptors for viral entry
What happens once the RNA genome of togaviruses enters the cytoplasm?
It is directly translated into viral proteins
How do flaviviruses and togaviruses enter cells?
Via receptor-mediated endocytosis within clathrin-coated vesicles
What is the function of NS3 protein in flaviviruses?
Is involved in polyprotein cleavage, RNA replicase component, nucleoside triphosphatase, and helicase activities
What is the diameter of naked icosahedral capsid of Picornaviruses?
30nm
What type of RNA genome do Picornaviruses possess?
'+' sense ssRNA
How many copies of VP4 are present in a mature Picornavirus virion?
40 copies
What is covalently bound to the 5’ end of the RNA in Picornaviruses?
$VPg$
Which segment of the influenza virus genome encodes for a single protein that is not an RNA polymerase subunit?
Segment 5
What is the total number of different viral proteins packaged by the influenza virus?
11
Which sequences are highly conserved and serve as universal primers in the influenza virus genome?
Uni-12 and Uni-13
What is the total number of different segments in the segmented negative sense ssRNA genome of the influenza virus?
$10-15$
What is the unique protein found in Filoviruses?
GP, a glycoprotein
Where are Capsid proteins palmitoylated in Filoviruses?
Golgi
What is the consequence of Ebola virus outbreaks?
Severe, often fatal disease
What is the genome size of Marburg virus?
$ ext{15-19 kb}$
How are Filovirus infections among humans primarily transmitted?
Physical contact with secretions/excretions
Which family does the Ebola virus belong to?
Filoviridae
What is the role of the precursor membrane protein (prM) in flaviviruses?
Promotion of viral budding
What process does Ebola virus use to produce two glycoproteins from the same gene?
RNA editing
What is involved in Flavivirus virion assembly?
Promotion by precursor membrane protein (prM)
Which cellular receptor does Filovirus GP bind to for attachment and entry?
NPC1 receptor
How is sGP released from infected cells and what is its potential function?
Released via proteolytic cleavage and serves as a biomarker and vaccine/antiviral target
What is the role of VP30 in Ebola virus infection?
Activates viral mRNA synthesis by reversing the inhibitory effect of a stem-loop structure at the beginning of the NP gene
Which family does the Ebola virus belong to, and what are some symptoms of infections from this family?
Belongs to Orthomyxoviridae; symptoms include high fever, sore throat, cough, headache, and muscular pain
What is the potential consequence for survivors of Ebola virus infection?
Latent infection with periodic spikes in EBOV antibodies, suggesting potential disease recrudescence
What are some symptoms of Orthomyxoviridae infections, and who is most at risk?
Symptoms include high fever, sore throat, cough, headache, and muscular pain; most fatal in elderly, infants, and chronically ill individuals
How does the Ebola virus enter cells?
Via micropinocytosis and fuses within vesicles using its fusion peptide
Which protein of flaviviruses is a multifunctional viral serine proteinase involved in polyprotein cleavage, RNA replicase component, nucleoside triphosphatase, and helicase activities?
NS3 protein
How do flaviviruses primarily enter cells?
Receptor-mediated endocytosis via clathrin-coated vesicles
What is the role of the precursor membrane protein (prM) in flaviviruses?
Protection of E protein from premature conformational changes
What is the genome type of togaviruses?
'+' sense single-stranded RNA
What triggers the fusion and release of the nucleocapsid of flaviviruses and togaviruses in the cell?
$pH$ changes in the cytoplasm
What is the cellular receptor to which the E glycoprotein of togaviruses binds for entry into cells?
Laminin receptor
What is involved in the entry of poliovirus RNA into the cytoplasm?
Receptor-mediated endocytosis via clathrin-coated vesicles
What is unique about the genome size of togaviruses?
Approximately 9.7-11.8kb in size
What is the function of NS3 protein in flaviviruses?
Polyprotein cleavage and RNA replicase activity
Where does replication occur for Ebola virus?
Cytoplasm
How are structural proteins generated in Filoviruses?
Polyprotein cleavage
Study Notes
Flavivirus and Togavirus: Structure and Entry
- NS3 protein is a multifunctional viral serine proteinase involved in polyprotein cleavage, RNA replicase component, nucleoside triphosphatase, and helicase activities.
- Synthesis of non-structural protein establishes active RNA replicase complexes, carried out on membranes in the cytoplasm, requiring the synthesis of a complementary copy (minus-strand) of the plus-strand RNA and subsequent synthesis of new plus-strand (genomic RNA).
- Flaviviruses have no clearly identified cellular receptor and enter cells through endocytosis within clathrin-coated vesicles, with alternative entry mechanisms including antibody-dependent enhancement (ADE) causing severe diseases like dengue hemorrhagic fever.
- The E protein of flaviviruses is a type I membrane protein found as a dimer, with domain II forming a dimer interface and containing the hydrophobic fusion peptide, and domain III used for receptor binding.
- Following the capsid protein precursor, the precursor membrane protein (prM) associates with the E protein in the endoplasmic reticulum (ER) to form a heterodimer, protecting E from premature conformational changes.
- Togaviruses cause disease in animals and humans, spreading through mosquitoes, with symptoms ranging from rashes, high fever, joint pain to encephalitis.
- Togaviruses have a spherical enveloped particle with a fringe of projections, arranged in icosahedral symmetry, with 240 heterodimers of glycoproteins E1 and E2 in the envelope and 240 copies of capsid proteins.
- Togaviruses have a linear ‘+’ sense single-stranded RNA genome, approximately 9.7-11.8kb in size, with both 5’ methylated cap and a 3’ poly(A) tail.
- The E glycoprotein of togaviruses binds to cellular receptors, such as laminin receptor, leading to receptor-mediated endocytosis via clathrin-coated vesicles.
- Once inside the cytoplasm, the RNA genome of togaviruses is released to be translated, interacting with cellular proteins to release the genome, catalyzed by partly cleaved non-structural proteins including nsP1, nsP2, and nsP4.
- The RNA polymerase of togaviruses can stop at a specific codon, potentially yielding protein123.
- Entry and fusion mechanisms of flaviviruses and togaviruses involve conformational changes in viral proteins in response to pH changes, leading to fusion and release of the nucleocapsid in the cell.
Flavivirus and Togavirus: Structure and Entry
- NS3 protein is a multifunctional viral serine proteinase involved in polyprotein cleavage, RNA replicase component, nucleoside triphosphatase, and helicase activities.
- Synthesis of non-structural protein establishes active RNA replicase complexes, carried out on membranes in the cytoplasm, requiring the synthesis of a complementary copy (minus-strand) of the plus-strand RNA and subsequent synthesis of new plus-strand (genomic RNA).
- Flaviviruses have no clearly identified cellular receptor and enter cells through endocytosis within clathrin-coated vesicles, with alternative entry mechanisms including antibody-dependent enhancement (ADE) causing severe diseases like dengue hemorrhagic fever.
- The E protein of flaviviruses is a type I membrane protein found as a dimer, with domain II forming a dimer interface and containing the hydrophobic fusion peptide, and domain III used for receptor binding.
- Following the capsid protein precursor, the precursor membrane protein (prM) associates with the E protein in the endoplasmic reticulum (ER) to form a heterodimer, protecting E from premature conformational changes.
- Togaviruses cause disease in animals and humans, spreading through mosquitoes, with symptoms ranging from rashes, high fever, joint pain to encephalitis.
- Togaviruses have a spherical enveloped particle with a fringe of projections, arranged in icosahedral symmetry, with 240 heterodimers of glycoproteins E1 and E2 in the envelope and 240 copies of capsid proteins.
- Togaviruses have a linear ‘+’ sense single-stranded RNA genome, approximately 9.7-11.8kb in size, with both 5’ methylated cap and a 3’ poly(A) tail.
- The E glycoprotein of togaviruses binds to cellular receptors, such as laminin receptor, leading to receptor-mediated endocytosis via clathrin-coated vesicles.
- Once inside the cytoplasm, the RNA genome of togaviruses is released to be translated, interacting with cellular proteins to release the genome, catalyzed by partly cleaved non-structural proteins including nsP1, nsP2, and nsP4.
- The RNA polymerase of togaviruses can stop at a specific codon, potentially yielding protein123.
- Entry and fusion mechanisms of flaviviruses and togaviruses involve conformational changes in viral proteins in response to pH changes, leading to fusion and release of the nucleocapsid in the cell.
Test your knowledge about the protein synthesis process of a virus. Learn about the generation and cleavage of a polyprotein, post-translational modifications, and the binding of capsid protein to the genome RNA packaging signal.
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