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
