35 Questions
What type of proteins are generally involved in mediating membrane fusion?
Type I transmembrane proteins
How is energy involved in the fusion process mediated by viral fusion proteins?
Conformation changes lead to the presence of energy, and fusion occurs without the need for ATP/metabolic energy
What role do fusion proteins play in viral infection?
They play a critical role in viral infection and can be therapeutic targets
What are the characteristics of Class II fusion proteins?
Mostly beta-sheets, tend to form dimers, and involve rearrangement of multimers of protein subunits with minor conformational changes at tertiary level
Which part of the nascent RNA chain forms RNA-RNA hybrids at 5’ TRS?
End of the leader sequence
What can lead to template switch if polymerase fails to find another template after dissociation?
Recombination between viral genomes
Where does the assembly of virions take place?
Endoplasmic reticulum Golgi intermediate compartment (ERGIC)
Which proteins play important roles in the formation of virus envelopes by budding?
M and E proteins
What interacts with packaging signals in N to ensure only full-length viral RNA gets packaged into virions?
$3’$ end of the cytoplasmic tail of M protein
Where are mature virions packaged before being transported to the cell surface for release?
Golgi membrane
What is responsible for incorporating HE (if present) and S into the membrane?
M protein
What plays a crucial role in mediating transport, processing, and modification of proteins in ERGIC?
M protein
What may help with genome repair and/or generate new viral strains/variants?
Recombination between viral genomes due to template switching
Which protein is responsible for viral entry and tropism, and is targeted by neutralizing antibodies and T-cells in infection?
Spike protein
What is the composition of the replicase gene (gene 1)?
ORF1a and ORF1b partially overlapping reading frames
Which cellular receptors do spike proteins bind to?
Aminopeptidase-N, sialic acid, ACE2, L-SIGN, TMPRSS2
What is the common membrane association for viral RNA synthesis among '+' strand RNA viruses of eukaryotes?
Membrane association of viral RNA synthesis
What is the structure of coronavirus nucleocapsids?
Formed from viral N-protein bound to viral RNA in a helical fashion
What is the role of the M-protein in some coronaviruses?
Forming a spherical core structure containing an internal helical nucleocapsid
What are the components of corona virions' envelope proteins?
Spike (S), membrane (M), envelope (E), nucleocapsid (N), and in some cases HE (hemagglutinin esterase) protein
What happens after fusion mediated by spike proteins?
Viral proteins are synthesized that organize and catalyze viral RNA synthesis
Where are replication complexes commonly observed for coronaviruses?
On double membrane vesicles by EM
How does genome replication proceed for coronaviruses?
Via a full-length negative-strand intermediate, and subgenomic mRNAs are transcribed from subgenomic negative strand mRNA templates
What assists with replication and packaging of the viral genome in coronaviruses?
RNA helicase and nucleoside triphosphatase
How do non-enveloped viruses penetrate host membranes?
By utilizing cellular transport systems
Where do many DNA viruses use for replication and latency establishment?
Nucleus
What is a target for antiviral drugs in virus replication cycle?
Every step in the virus replication cycle
How can viruses enter the nucleus?
During mitosis
What are some ways to prevent virus entry into host cells?
Neutralizing antibodies and receptor occupation
What is targeted by antiviral strategies during virus internalization?
Cellular processes for internalization
What process do antiviral strategies target related to membrane fusion?
Membrane fusion
What are the advantages of narrow spectrum antivirals?
Reduced likelihood of resistance development
What are the disadvantages of broad spectrum antivirals?
Increased risk of side effects
What is a characteristic of coronaviruses regarding their structure?
Enveloped with helical capsid
What is a key feature of SARS and COVID-19?
Airborne transmission
Study Notes
Virus Replication and Antiviral Strategies
- Non-enveloped viruses penetrate host membranes without lysis or rupture
- Viruses utilize cellular transport systems for efficient transport to the cytosol
- Many DNA viruses use the nucleus for replication and can establish latency
- Strategies for viruses to pass through the nuclear membrane
- Various ways for viruses to enter the nucleus, including during mitosis
- Every step in the virus replication cycle is a target for antiviral drugs
- Different ways to prevent virus entry, including neutralizing antibodies and receptor occupation
- Specific inhibitors and agents used to interfere with cellular processes for internalization
- Antiviral strategies targeting membrane fusion and uncoating of capsids
- Advantages and disadvantages of narrow and broad spectrum antivirals
- Characteristics of coronaviruses, including structure and genome
- Overview of the history, impact, and characteristics of SARS and COVID-19
Test your knowledge about the structural components of coronavirus virions, including nucleocapsids, core structure, and envelope proteins.
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