Viral Pathogens: Classification, Biology, Diseases I Flashcards
What are the two types of virus?
RNA
DNA
What are the four structures of viral genomes?
SsRNA
DsRNA
SsDNA
DsDNA
What are the structure of RNA genomes?
Linear and segmented
What are the structure of DNA genomes?
Linear or circular
What is the central dogma?
DNA polymerase facilitates replication
RNA polymerase facilitates transcription
Ribosomes facilitate translation
How do viruses use the central dogma?
Reverse transcriptase reverses RNA polymerase
RNA dependant RNA polymerase reverses RNA replication
What is the baltimore classification?
Classes of genetic material present in the virion
What are group I viruses made up of?
DNA +/-
What are group II viruses made up of?
DNA+
What are group III viruses made up of?
RNA +/-
What are group IV viruses made up of?
RNA+
What are group V viruses made up of?
RNA -
What are group VI viruses made up of?
RNA+
What are group VII viruses made up of?
DNA+/-
What does the HIV-1 outer envelope consist of?
Lipid bilayer with protruding Env spikes
What lies inside the HIV-1 envelope?
Shells of Gag proteins
What associates with the membrane?
Matrix
What does the capsid form?
Conical capsid
What does the viral RNA genome form?
Nucleocapsid
What does the envelope consist of and covered by?
A trimer of gp41 and gp120 peptide subunits
Covered with glycans
What are the two membrane proteins necessary for HIV-1?
CD4 and a chemokine receptor
What are the steps in HIV entry?
Native primer
CD4 binding and T20 binding site exposure (due to a conformational change)
CoR binding and fusion peptide insertion
6-helix bundle formation and membrane fusion
What is HIV-1 tropic for?
CD4 expressing cells
What are the early phases of HIV-1 infection?
Fusion
Uncoating and reverse transcription
Intracellular trafficking
Nuclear entry
What is reverse transcriptase a heterodimer of?
P66 and p51 subunits
What are the three enzymatic properties of reverse transcriptase?
RNA dependant DNA polymerase
RNAse H
DNA dependant DNA polymerase
What is reverse transcription mediated by?
Reverse transcriptase
What does reverse transcriptase act as?
Polymerase to make the RNA template from the RNA genome
How does the HIV DNA insert itself into the host chromosome?
Ends of viral DNA have specific sequences that are recognised by integrase enzymes
Sticks and pastes the viral DNA into cellular DNA
How does the integrase enzyme Stick and paste the viral DNA into cellular DNA?
Bending the viral DNA round into very close contact with the cellular DNA
What binds HIV-1 integrase and facilitates chromatin targeting?
LEDGF/P75
What does the HIV-1 promoter contain?
Binding sites for transcription factors that are present in T-lymphocytes
What does the HIV-1 promoter do?
Recruits cellular proteins to the viral genome that are required for mRNA transcription
What is the first thing that gets produced by the genome and what does it do?
Tat protein
Specifically binds to the RNA and enhances RNA replication
What does the HIV-1 rev protein mediate?
Nuclear export of a spliced viral RNA
What does HIV-1 rev protein form?
A feedback loop wherein it comes back into the nucleus and promotes the nuclear export of the RNA viral genome over cellular RNA
What does REV protein interact with to promote viral genome replication?
Crm 1 and RRE RNA
What does dimerisation of the un spliced viral RNA allow?
Packing of two genomes in the virus
What is the kissing loop complex?
Two of the same sequence brought together
What is gag-pol protein generated by?
7 ribosomal frameshifting induced by a slippery sequence on RNA hairpin structure
What is myristoylation?
Post-translational modification of glycines in the MA domain of Gag
What does myristoylation mediate?
Association with the plasma membrane
What causes the polyprotein to be made, myristoylated and transferred to the cell surface?
Tsg 101
What is hijacked by HIV to perform membrane abscission during viral release?
ESCRT
What is abscission?
Combining proteins and RNAs into a capsid, which essentially pushes the new capsid into the extracellular space
What does Gag processing generate?
Mature viruses
