Lecture 8 2/12/24 Flashcards
What are the general characteristics of (-) strand RNA genomes?
-complementary to mRNA
-coated with nucleocapsid
-used as templates for synthesizing new RNA molecules with RdRp
What are the general characteristics of (+) strand RNA genomes?
-the same as mRNA used to produce viral proteins
-not coated with protein/naked
What are the general characteristics of dsRNA genomes?
-double helix structure
-naked
-RdRp involved in replication
-one strand used as template to produce another (+) or (-) sense genome
What are the characteristics of the nucleocapsid?
-protein coat that encapsulates viral RNA genome in a compact structure
-protects RNA genome from host cell enzymes
-facilitates viral replication and assembly
What are the rules for viral RNA synthesis?
-genome must be copied end to end with no loss of nucleotide sequence
-viral mRNAs must be produced that can be efficiently translated by cellular protein synthesis machinery
What are the universal rules for RNA-directed RNA synthesis?
-initiates and terminates at specific sites on the template
-synthesis initiated either de novo or via primer
-other viral and cell proteins may be required
-synthesized by template-directed stepwise incorporation of nucleotides in 5’-3’ direction
What are the two modes of RNA synthesis initiation?
-de novo/directly begun at 3’ end of the template
-primer-dependent
What are the characteristics of the two-metal mechanism for polymerase catalysis?
-catalytic center of RdRp is coordinated by magnesium-amino acid complex
-ensures the accurate copying of RNA genome and efficient translation of the produced mRNA
What are the characteristics of the poliovirus RdRp?
-highly conserved enzyme
-highly conserved active site responsible for catalysis of RNA synthesis
What are the characteristics of picornaviruses?
-(+)ssRNA genome
-non-enveloped
-icosahedral capsid
What are examples of animal picornaviruses?
-foot-and-mouth disease virus
-swine vesicular disease virus
-equine rhinitis A virus
-Seneca Valley virus
What are the cellular effects of picornaviruses?
-stimulates IFN
-inhibits RNA synthesis of cells
-toxic effects of coat proteins
-altered plasma membrane permeability
-interference with cellular translation
What are the characteristics of flaviviruses?
-(+)ssRNA genome
-icosahedral capsid
-enveloped
What are examples of animal flaviviruses?
-tick-borne encephalitis virus
-louping ill virus
-Powassan virus
What are the steps of the flavivirus lifecycle?
-attachment and entry: binding to specific receptors triggers endocytosis
-uncoating: release of viral RNA into cytoplasm
-translation: translation of viral RNA via host cell ribosomes to produce single polyprotein
-cleavage: cleavage of polyprotein into functional proteins
-RNA replication: RdRp replication of viral RNA genome
-assembly: new viral particles assembled by host cell
-release: cell lysis or budding
What are the characteristics of arboviruses?
-vectored, often by mosquitoes
-emerging threat in tropical/subtropical regions
What are the characteristics of alphaviruses?
-(+)ssRNA
-enveloped
What are examples of animal alphaviruses?
-Sindbis virus
-equine encephalitis virus
Which protein is involved in alphavirus attachment to the host cell?
E1
Which protein is involved with alphavirus fusion to the host cell and viral genome release?
E2
What are the characteristics of caliciviruses?
-icosahedral capsid
-non-enveloped
-(+)ssRNA genome
What are examples of animal caliciviruses?
-vesicular exanthema of swine
-rabbit hemorrhagic disease virus
-feline calicivirus
What are the characteristics of coronaviruses?
-(+)ssRNA genome
-largest animal virus genome
-helical symmetry
-enveloped
How does translation of alphaviruses differ from flaviviruses and picornaviruses?
only some of the viral genome undergoes translation in alphaviruses
